diff --git a/TrungPH/ex1.ts b/TrungPH/ex1.ts
new file mode 100644
index 0000000..661bd87
--- /dev/null
+++ b/TrungPH/ex1.ts
@@ -0,0 +1,25 @@
+interface User {
+    name: string;
+    age: number;
+    occupation: string;
+}
+
+export const users: User[] = [
+    {
+        name: 'Max Mustermann',
+        age: 25,
+        occupation: 'Chimney sweep'
+    },
+    {
+        name: 'Kate Müller',
+        age: 23,
+        occupation: 'Astronaut'
+    }
+];
+
+export function logPerson(user: User) {
+    console.log(` - ${user.name}, ${user.age}`);
+}
+
+console.log('Users:');
+users.forEach(logPerson);
diff --git a/TrungPH/ex10.ts b/TrungPH/ex10.ts
new file mode 100644
index 0000000..22ffe6e
--- /dev/null
+++ b/TrungPH/ex10.ts
@@ -0,0 +1,117 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+type Person = User | Admin;
+
+const admins: Admin[] = [
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' }
+];
+
+const users: User[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' }
+];
+
+export type ApiResponse<T> = (
+  {
+      status: 'success';
+      data: T;
+  } |
+  {
+      status: 'error';
+      error: string;
+  }
+);
+
+type callbackFunction<T> = (callback: (response: ApiResponse<T>) => void) => void;
+type promiseFunction<T> = () => Promise<T>;
+
+export function promisify<T>(fn: callbackFunction<T>): promiseFunction<T> {
+    return () => new Promise<T>((resolve, reject) => {
+        fn((response) => {
+            if (response.status === 'success') {
+                resolve(response.data);
+            } else {
+                reject(new Error(response.error));
+            }
+        });
+    });
+}
+
+const oldApi = {
+  requestAdmins(callback: (response: ApiResponse<Admin[]>) => void) {
+      callback({
+          status: 'success',
+          data: admins
+      });
+  },
+  requestUsers(callback: (response: ApiResponse<User[]>) => void) {
+      callback({
+          status: 'success',
+          data: users
+      });
+  },
+  requestCurrentServerTime(callback: (response: ApiResponse<number>) => void) {
+      callback({
+          status: 'success',
+          data: Date.now()
+      });
+  },
+  requestCoffeeMachineQueueLength(callback: (response: ApiResponse<number>) => void) {
+      callback({
+          status: 'error',
+          error: 'Numeric value has exceeded Number.MAX_SAFE_INTEGER.'
+      });
+  }
+};
+
+export const api = {
+  requestAdmins: promisify(oldApi.requestAdmins),
+  requestUsers: promisify(oldApi.requestUsers),
+  requestCurrentServerTime: promisify(oldApi.requestCurrentServerTime),
+  requestCoffeeMachineQueueLength: promisify(oldApi.requestCoffeeMachineQueueLength)
+};
+
+function logPerson(person: Person) {
+  console.log(
+      ` - ${person.name}, ${person.age}, ${person.type === 'admin' ? person.role : person.occupation}`
+  );
+}
+
+async function startTheApp() {
+  console.log('Admins:');
+  (await api.requestAdmins()).forEach(logPerson);
+  console.log();
+
+  console.log('Users:');
+  (await api.requestUsers()).forEach(logPerson);
+  console.log();
+
+  console.log('Server time:');
+  console.log(`   ${new Date(await api.requestCurrentServerTime()).toLocaleString()}`);
+  console.log();
+
+  console.log('Coffee machine queue length:');
+  console.log(`   ${await api.requestCoffeeMachineQueueLength()}`);
+}
+
+startTheApp().then(
+  () => {
+      console.log('Success!');
+  },
+  (e: Error) => {
+      console.log(`Error: "${e.message}", but it's fine, sometimes errors are inevitable.`);
+  }
+);
diff --git a/TrungPH/ex11.d.ts b/TrungPH/ex11.d.ts
new file mode 100644
index 0000000..e6ff463
--- /dev/null
+++ b/TrungPH/ex11.d.ts
@@ -0,0 +1,41 @@
+
+declare module 'str-utils' {
+  // export const ...
+  // export function ...
+
+  /**
+* Reverses a string.
+* @param {String} value
+* @return {String}
+*/
+export function strReverse(value: string): string;
+
+/**
+* Converts a string to lower case.
+* @param {String} value
+* @return {String}
+*/
+export function strToLower(value: string): string;
+
+/**
+* Converts a string to upper case.
+* @param {String} value
+* @return {String}
+*/
+export function strToUpper(value: string): string;
+
+/**
+* Randomizes characters of a string.
+* @param {String} value
+* @return {String}
+*/
+export function strRandomize(value: string): string;
+
+/**
+* Inverts case of a string.
+* @param {String} value
+* @return {String}
+*/
+export function strInvertCase(value: string): string;
+
+}
diff --git a/TrungPH/ex12.d.ts b/TrungPH/ex12.d.ts
new file mode 100644
index 0000000..b8319ef
--- /dev/null
+++ b/TrungPH/ex12.d.ts
@@ -0,0 +1,17 @@
+declare module 'stats' {
+  type Comparator<T> = (a: T, b: T) => number;
+  type GetIndex = <T>(input: T[], comparator: Comparator<T>) => number;
+
+  export const getMinIndex: GetIndex;
+  export const getMedianIndex: GetIndex;
+  export const getMaxIndex: GetIndex;
+
+
+  type GetElement = <T>(input: T[], comparator: Comparator<T>) => null | T;
+  
+  export const getMinElement: GetElement;
+  export const getMedianElement: GetElement;
+  export const getMaxElement: GetElement;
+
+  export const getAverageValue: <T>(input: T[], getValue: (item: T) => number) => number | null;
+}
diff --git a/TrungPH/ex13.d.ts b/TrungPH/ex13.d.ts
new file mode 100644
index 0000000..aaf86bc
--- /dev/null
+++ b/TrungPH/ex13.d.ts
@@ -0,0 +1,12 @@
+// This enables module augmentation mode.
+import 'date-wizard';
+
+declare module 'date-wizard' {
+    interface DateDetails {
+        hours: number;
+        minutes: number,
+        seconds: number
+    }
+
+    function pad(input: number): string
+}
diff --git a/TrungPH/ex2.ts b/TrungPH/ex2.ts
new file mode 100644
index 0000000..39b3a15
--- /dev/null
+++ b/TrungPH/ex2.ts
@@ -0,0 +1,42 @@
+interface User {
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+export const persons: Person[] = [
+  {
+      name: 'Max Mustermann',
+      age: 25,
+      occupation: 'Chimney sweep'
+  },
+  {
+      name: 'Jane Doe',
+      age: 32,
+      role: 'Administrator'
+  },
+  {
+      name: 'Kate Müller',
+      age: 23,
+      occupation: 'Astronaut'
+  },
+  {
+      name: 'Bruce Willis',
+      age: 64,
+      role: 'World saver'
+  }
+];
+
+export function logPerson(person: Person) {
+  console.log(` - ${person.name}, ${person.age}`);
+}
+
+persons.forEach(logPerson);
diff --git a/TrungPH/ex3.ts b/TrungPH/ex3.ts
new file mode 100644
index 0000000..1279874
--- /dev/null
+++ b/TrungPH/ex3.ts
@@ -0,0 +1,54 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+export const persons: Person[] = [
+  {
+      type: 'user',
+      name: 'Max Mustermann',
+      age: 25,
+      occupation: 'Chimney sweep'
+  },
+  {
+      type: 'admin',
+      name: 'Jane Doe',
+      age: 32,
+      role: 'Administrator'
+  },
+  {
+      type: 'user',
+      name: 'Kate Müller',
+      age: 23,
+      occupation: 'Astronaut'
+  },
+  {
+      type: 'admin',
+      name: 'Bruce Willis',
+      age: 64,
+      role: 'World saver'
+  }
+];
+
+export function logPerson(person: Person) {
+  let additionalInformation: string;
+  if (person.type === 'admin') {
+      additionalInformation = person.role;
+  } else {
+      additionalInformation = person.occupation;
+  }
+  console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
+}
+
+persons.forEach(logPerson);
diff --git a/TrungPH/ex4.ts b/TrungPH/ex4.ts
new file mode 100644
index 0000000..a53e841
--- /dev/null
+++ b/TrungPH/ex4.ts
@@ -0,0 +1,49 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+export const persons: Person[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' }
+];
+
+export function isAdmin(person: Person): person is Admin {
+  return person.type === 'admin';
+}
+
+export function isUser(person: Person):  person is User {
+  return person.type === 'user';
+}
+
+export function logPerson(person: Person) {
+  let additionalInformation: string = '';
+  if (isAdmin(person)) {
+    additionalInformation = person.role;
+  }
+  if (isUser(person)) {
+    additionalInformation = person.occupation;
+  }
+  console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
+}
+
+console.log('Admins:');
+persons.filter(isAdmin).forEach(logPerson);
+
+console.log();
+
+console.log('Users:');
+persons.filter(isUser).forEach(logPerson);
\ No newline at end of file
diff --git a/TrungPH/ex5.ts b/TrungPH/ex5.ts
new file mode 100644
index 0000000..a323ede
--- /dev/null
+++ b/TrungPH/ex5.ts
@@ -0,0 +1,58 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+export const persons: Person[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' },
+  { type: 'user', name: 'Wilson', age: 23, occupation: 'Ball' },
+  { type: 'admin', name: 'Agent Smith', age: 23, role: 'Administrator' }
+];
+
+export const isAdmin = (person: Person): person is Admin => person.type === 'admin';
+export const isUser = (person: Person): person is User => person.type === 'user';
+
+export function logPerson(person: Person) {
+  let additionalInformation = '';
+  if (isAdmin(person)) {
+      additionalInformation = person.role;
+  }
+  if (isUser(person)) {
+      additionalInformation = person.occupation;
+  }
+  console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
+}
+
+export function filterUsers(persons: Person[], criteria?: Partial<User>): User[] {
+  if (!criteria) return persons.filter(isUser); // return all users if no criteria is specified
+
+  return persons.filter(isUser).filter((user) => {
+      const criteriaKeys = Object.keys(criteria) as (keyof User)[];
+      return criteriaKeys.every((fieldName) => {
+          return user[fieldName] === criteria[fieldName];
+      });
+  });
+}
+
+console.log('Users of age 23:');
+
+filterUsers(
+  persons,
+  {
+      age: 23
+  }
+).forEach(logPerson);
diff --git a/TrungPH/ex6.ts b/TrungPH/ex6.ts
new file mode 100644
index 0000000..a5b9430
--- /dev/null
+++ b/TrungPH/ex6.ts
@@ -0,0 +1,54 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+export const persons: Person[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' },
+  { type: 'user', name: 'Wilson', age: 23, occupation: 'Ball' },
+  { type: 'admin', name: 'Agent Smith', age: 23, role: 'Anti-virus engineer' }
+];
+
+export function logPerson(person: Person) {
+  console.log(
+      ` - ${person.name}, ${person.age}, ${person.type === 'admin' ? person.role : person.occupation}`
+  );
+}
+
+export function filterPersons(persons: Person[], personType: User['type'], criteria: Partial<Omit<User, 'type'>>): User[];
+export function filterPersons(persons: Person[], personType: Admin['type'], criteria: Partial<Omit<Admin, 'type'>>): Admin[];
+export function filterPersons(persons: Person[], personType: string, criteria: Partial<Person>): Person[] {
+  return persons
+      .filter((person) => person.type === personType)
+      .filter((person) => {
+          let criteriaKeys = Object.keys(criteria) as (keyof Person)[];
+          return criteriaKeys.every((fieldName) => {
+              return person[fieldName] === criteria[fieldName];
+          });
+      });
+}
+
+export const usersOfAge23 = filterPersons(persons, 'user', { age: 23 });
+export const adminsOfAge23 = filterPersons(persons, 'admin', { age: 23 });
+
+console.log('Users of age 23:');
+usersOfAge23.forEach(logPerson);
+
+console.log();
+
+console.log('Admins of age 23:');
+adminsOfAge23.forEach(logPerson);
diff --git a/TrungPH/ex7.ts b/TrungPH/ex7.ts
new file mode 100644
index 0000000..9fb334b
--- /dev/null
+++ b/TrungPH/ex7.ts
@@ -0,0 +1,96 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+export type Person = User | Admin;
+
+function logUser(user: User) {
+  const pos = users.indexOf(user) + 1;
+  console.log(` - #${pos} User: ${user.name}, ${user.age}, ${user.occupation}`);
+}
+
+function logAdmin(admin: Admin) {
+  const pos = admins.indexOf(admin) + 1;
+  console.log(` - #${pos} Admin: ${admin.name}, ${admin.age}, ${admin.role}`);
+}
+
+const admins: Admin[] = [
+  {
+      type: 'admin',
+      name: 'Will Bruces',
+      age: 30,
+      role: 'Overseer'
+  },
+  {
+      type: 'admin',
+      name: 'Steve',
+      age: 40,
+      role: 'Steve'
+  }
+];
+
+const users: User[] = [
+  {
+      type: 'user',
+      name: 'Moses',
+      age: 70,
+      occupation: 'Desert guide'
+  },
+  {
+      type: 'user',
+      name: 'Superman',
+      age: 28,
+      occupation: 'Ordinary person'
+  }
+];
+
+export function swap<Input1, Input2>(v1: Input1, v2: Input2): [Input2, Input1] {
+  return [v2, v1];
+}
+
+function test1() {
+  console.log('test1:');
+  const [secondUser, firstAdmin] = swap(admins[0], users[1]);
+  logUser(secondUser);
+  logAdmin(firstAdmin);
+}
+
+function test2() {
+  console.log('test2:');
+  const [secondAdmin, firstUser] = swap(users[0], admins[1]);
+  logAdmin(secondAdmin);
+  logUser(firstUser);
+}
+
+function test3() {
+  console.log('test3:');
+  const [secondUser, firstUser] = swap(users[0], users[1]);
+  logUser(secondUser);
+  logUser(firstUser);
+}
+
+function test4() {
+  console.log('test4:');
+  const [firstAdmin, secondAdmin] = swap(admins[1], admins[0]);
+  logAdmin(firstAdmin);
+  logAdmin(secondAdmin);
+}
+
+function test5() {
+  console.log('test5:');
+  const [stringValue, numericValue] = swap(123, 'Hello World');
+  console.log(` - String: ${stringValue}`);
+  console.log(` - Numeric: ${numericValue}`);
+}
+
+[test1, test2, test3, test4, test5].forEach((test) => test());
diff --git a/TrungPH/ex8.ts b/TrungPH/ex8.ts
new file mode 100644
index 0000000..cc2b07d
--- /dev/null
+++ b/TrungPH/ex8.ts
@@ -0,0 +1,72 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+type PowerUser = Omit<User, 'type'> & Omit<Admin, 'type'> & {
+  type: 'powerUser';
+};
+
+export type Person = User | Admin | PowerUser;
+
+export const persons: Person[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' },
+  {
+      type: 'powerUser',
+      name: 'Nikki Stone',
+      age: 45,
+      role: 'Moderator',
+      occupation: 'Cat groomer'
+  }
+];
+
+function isAdmin(person: Person): person is Admin {
+  return person.type === 'admin';
+}
+
+function isUser(person: Person): person is User {
+  return person.type === 'user';
+}
+
+function isPowerUser(person: Person): person is PowerUser {
+  return person.type === 'powerUser';
+}
+
+export function logPerson(person: Person) {
+  let additionalInformation: string = '';
+  if (isAdmin(person)) {
+      additionalInformation = person.role;
+  }
+  if (isUser(person)) {
+      additionalInformation = person.occupation;
+  }
+  if (isPowerUser(person)) {
+      additionalInformation = `${person.role}, ${person.occupation}`;
+  }
+  console.log(`${person.name}, ${person.age}, ${additionalInformation}`);
+}
+
+console.log('Admins:');
+persons.filter(isAdmin).forEach(logPerson);
+
+console.log();
+
+console.log('Users:');
+persons.filter(isUser).forEach(logPerson);
+
+console.log();
+
+console.log('Power users:');
+persons.filter(isPowerUser).forEach(logPerson);
diff --git a/TrungPH/ex9.ts b/TrungPH/ex9.ts
new file mode 100644
index 0000000..0dc781f
--- /dev/null
+++ b/TrungPH/ex9.ts
@@ -0,0 +1,129 @@
+interface User {
+  type: 'user';
+  name: string;
+  age: number;
+  occupation: string;
+}
+
+interface Admin {
+  type: 'admin';
+  name: string;
+  age: number;
+  role: string;
+}
+
+type Person = User | Admin;
+
+const admins: Admin[] = [
+  { type: 'admin', name: 'Jane Doe', age: 32, role: 'Administrator' },
+  { type: 'admin', name: 'Bruce Willis', age: 64, role: 'World saver' }
+];
+
+const users: User[] = [
+  { type: 'user', name: 'Max Mustermann', age: 25, occupation: 'Chimney sweep' },
+  { type: 'user', name: 'Kate Müller', age: 23, occupation: 'Astronaut' }
+];
+
+export type ApiResponse<T> = (
+  {
+      status: 'success';
+      data: T;
+  } |
+  {
+      status: 'error';
+      error: string;
+  }
+);
+
+type AdminsApiResponse =  ApiResponse<Admin[]>;
+
+type UsersApiResponse = ApiResponse<User[]>;
+
+export function requestAdmins(callback: (response: AdminsApiResponse) => void) {
+  callback({
+      status: 'success',
+      data: admins
+  });
+}
+
+export function requestUsers(callback: (response: UsersApiResponse) => void) {
+  callback({
+      status: 'success',
+      data: users
+  });
+}
+
+export function requestCurrentServerTime(callback: (response: ApiResponse<number>) => void) {
+  callback({
+      status: 'success',
+      data: Date.now()
+  });
+}
+
+export function requestCoffeeMachineQueueLength(callback: (response: ApiResponse<number>) => void) {
+  callback({
+      status: 'error',
+      error: 'Numeric value has exceeded Number.MAX_SAFE_INTEGER.'
+  });
+}
+
+function logPerson(person: Person) {
+  console.log(
+      ` - ${person.name}, ${person.age}, ${person.type === 'admin' ? person.role : person.occupation}`
+  );
+}
+
+function startTheApp(callback: (error: Error | null) => void) {
+  requestAdmins((adminsResponse) => {
+      console.log('Admins:');
+      if (adminsResponse.status === 'success') {
+          adminsResponse.data.forEach(logPerson);
+      } else {
+          return callback(new Error(adminsResponse.error));
+      }
+
+      console.log();
+
+      requestUsers((usersResponse) => {
+          console.log('Users:');
+          if (usersResponse.status === 'success') {
+              usersResponse.data.forEach(logPerson);
+          } else {
+              return callback(new Error(usersResponse.error));
+          }
+
+          console.log();
+
+          requestCurrentServerTime((serverTimeResponse) => {
+              console.log('Server time:');
+              if (serverTimeResponse.status === 'success') {
+                  console.log(`   ${new Date(serverTimeResponse.data).toLocaleString()}`);
+              } else {
+                  return callback(new Error(serverTimeResponse.error));
+              }
+
+              console.log();
+
+              requestCoffeeMachineQueueLength((coffeeMachineQueueLengthResponse) => {
+                  console.log('Coffee machine queue length:');
+                  if (coffeeMachineQueueLengthResponse.status === 'success') {
+                      console.log(`   ${coffeeMachineQueueLengthResponse.data}`);
+                  } else {
+                      return callback(new Error(coffeeMachineQueueLengthResponse.error));
+                  }
+
+                  callback(null);
+              });
+          });
+      });
+  });
+}
+
+startTheApp((e: Error | null) => {
+  console.log();
+  if (e) {
+      console.log(`Error: "${e.message}", but it's fine, sometimes errors are inevitable.`)
+  } else {
+      console.log('Success!');
+  }
+});