diff --git a/client/src/app/core/core-services/action.service.ts b/client/src/app/core/core-services/action.service.ts
index 295b649014..7355fad03c 100644
--- a/client/src/app/core/core-services/action.service.ts
+++ b/client/src/app/core/core-services/action.service.ts
@@ -2,9 +2,30 @@ import { Injectable } from '@angular/core';
 
 import { HttpService } from './http.service';
 
-export interface RequestInfo {
+export interface ActionRequest {
     action: string;
-    data: any;
+    data: any[];
+}
+
+interface ActionResponse<T extends {}> {
+    success: true;
+    message: string;
+    results?: ((T | null)[] | null)[];
+}
+function isActionResponse<T extends {}>(obj: any): obj is ActionResponse<T> {
+    const response = obj as ActionResponse<T>;
+    return !!obj && response.success === true && !!response.message;
+}
+
+interface ActionError {
+    success: false;
+    message: string;
+    error_index?: number;
+}
+
+function isActionError(obj: any): obj is ActionError {
+    const response = obj as ActionError;
+    return !!obj && response.success === false && !!response.message;
 }
 
 @Injectable({
@@ -15,15 +36,39 @@ export class ActionService {
 
     private constructor(private http: HttpService) {}
 
-    public async sendRequest<T>(action: string, data: any): Promise<T> {
-        return this._sendRequest({ action, data: [data] });
+    public async sendRequest<T>(action: string, data: any): Promise<T | null> {
+        const results = await this._sendRequest<T>({ action, data: [data] });
+        if (!results) {
+            return null;
+        }
+        if (results.length !== 1) {
+            throw new Error('Inner resultlength is not 1 from the action service');
+        }
+        return results[0];
     }
 
-    public async sendBulkRequest<T>(action: string, data: any[]): Promise<T> {
-        return this._sendRequest({ action, data });
+    public async sendBulkRequest<T>(action: string, data: any[]): Promise<T[] | null> {
+        const results = await this._sendRequest<T>({ action, data });
+        if (results.length !== data.length) {
+            throw new Error(`Inner resultlength is not ${data.length} from the action service`);
+        }
+        return results;
     }
 
-    private async _sendRequest<T>(request: RequestInfo): Promise<T> {
-        return await this.http.post<T>(this.ACTION_URL, [request]);
+    private async _sendRequest<T>(request: ActionRequest): Promise<T[] | null> {
+        const response = await this.http.post<T>(this.ACTION_URL, [request]);
+        if (isActionError(response)) {
+            throw response.message;
+        } else if (isActionResponse<T>(response)) {
+            const results = response.results;
+            if (!results) {
+                return null;
+            }
+            if (results.length !== 1) {
+                throw new Error('Resultlength is not 1 from the action service');
+            }
+            return results[0];
+        }
+        throw new Error('Unknown return type from action service');
     }
 }
diff --git a/client/src/app/core/core-services/http.service.ts b/client/src/app/core/core-services/http.service.ts
index 2d311a0e16..7c05cf62a0 100644
--- a/client/src/app/core/core-services/http.service.ts
+++ b/client/src/app/core/core-services/http.service.ts
@@ -10,21 +10,7 @@ import { HttpOptions } from '../definitions/http-options';
 import { formatQueryParams, QueryParams } from '../definitions/query-params';
 import { toBase64 } from '../to-base64';
 
-export interface ErrorDetailResponse {
-    detail: string | string[];
-    args?: string[];
-}
-
-function isErrorDetailResponse(obj: any): obj is ErrorDetailResponse {
-    return (
-        obj &&
-        typeof obj === 'object' &&
-        (typeof obj.detail === 'string' || obj.detail instanceof Array) &&
-        (!obj.args || obj.args instanceof Array)
-    );
-}
-
-export interface ErrorMessageResponse {
+interface ErrorMessageResponse {
     message: string;
     success: boolean;
 }
@@ -142,27 +128,16 @@ export class HttpService {
             return error;
         }
 
-        if (e.status === 405) {
-            // this should only happen, if the url is wrong -> a bug.
-            error += this.translate.instant(
-                'The requested method is not allowed. Please contact your system administrator.'
-            );
-        } else if (!e.error) {
+        if (!e.error) {
             error += this.translate.instant("The server didn't respond.");
         } else if (typeof e.error === 'object') {
-            if (isErrorDetailResponse(e.error)) {
-                error += this.processErrorDetailResponse(e.error);
-            } else if (isErrorMessageResponse(e.error)) {
+            if (isErrorMessageResponse(e.error)) {
                 error += e.error.message;
             } else {
                 const errorList = Object.keys(e.error).map(key => {
                     const capitalizedKey = key.charAt(0).toUpperCase() + key.slice(1);
                     const message = e.error[key];
-                    if (typeof message === 'string') {
-                        return `${this.translate.instant(capitalizedKey)}: ${message}`;
-                    } else {
-                        return `${this.translate.instant(capitalizedKey)}: ${this.processErrorDetailResponse(message)}`;
-                    }
+                    return `${this.translate.instant(capitalizedKey)}: ${message}`;
                 });
                 error = errorList.join(', ');
             }
@@ -179,29 +154,6 @@ export class HttpService {
         return error;
     }
 
-    /**
-     * Errors from the servers may be string or array of strings. This function joins the strings together,
-     * if an array is send.
-     * @param str a string or a string array to join together.
-     * @returns Error text(s) as single string
-     */
-    private processErrorDetailResponse(response: ErrorDetailResponse): string {
-        let message: string;
-        if (response.detail instanceof Array) {
-            message = response.detail.join(' ');
-        } else {
-            message = response.detail;
-        }
-        message = this.translate.instant(message);
-
-        if (response.args && response.args.length > 0) {
-            for (let i = 0; i < response.args.length; i++) {
-                message = message.replace(`{${i}}`, response.args[i].toString());
-            }
-        }
-        return message;
-    }
-
     /**
      * Executes a get on a path with a certain object
      * @param path The path to send the request to.
diff --git a/client/src/app/core/repositories/base-repository.ts b/client/src/app/core/repositories/base-repository.ts
index 7b93a441b0..a3b496b7c5 100644
--- a/client/src/app/core/repositories/base-repository.ts
+++ b/client/src/app/core/repositories/base-repository.ts
@@ -340,11 +340,21 @@ export abstract class BaseRepository<V extends BaseViewModel, M extends BaseMode
         this.repositoryServiceCollector.errorService.showError(errorMessage);
     };
 
-    protected sendActionToBackend(action: string, payload: any): Promise<any> {
-        return this.actions.sendRequest(action, payload).catch(this.raiseError);
+    protected async sendActionToBackend(action: string, payload: any): Promise<any> {
+        try {
+            return await this.actions.sendRequest(action, payload);
+        } catch (e) {
+            this.raiseError(e);
+            throw e;
+        }
     }
 
-    protected sendBulkActionToBackend(action: string, payload: any[]): Promise<any> {
-        return this.actions.sendBulkRequest(action, payload).catch(this.raiseError);
+    protected async sendBulkActionToBackend(action: string, payload: any[]): Promise<any> {
+        try {
+            return await this.actions.sendBulkRequest(action, payload);
+        } catch (e) {
+            this.raiseError(e);
+            throw e;
+        }
     }
 }
diff --git a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
index 94910225db..9172dc396d 100644
--- a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
+++ b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
@@ -515,10 +515,8 @@ export class AssignmentDetailComponent extends BaseModelContextComponent impleme
      */
     public async createAssignment(): Promise<void> {
         try {
-            /*const response = */ await this.assignmentRepo.create(this.assignmentForm.value);
-            console.error('TODO: wait for returned id and navigate to it');
-            this.router.navigate([`./assignments/`]);
-            // this.router.navigate([`./assignments/${response.id}`]);
+            const response = await this.assignmentRepo.create(this.assignmentForm.value);
+            this.router.navigate([`./assignments/${response.id}`]);
         } catch (e) {
             this.raiseError(e);
         }