mat-tab-group 13 problems

[webspecialist]

I am using windows 10, node 16.13.2, npm 8.1.2, angular-cli 13.0.4.

I saw 13 problems, why is that?:

[{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "'mat-tab-group' is not a known element:\n1. If 'mat-tab-group' is an Angular component, then verify that it is part of this module.\n2. If 'mat-tab-group' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.",
	"source": "ng",
	"startLineNumber": 5,
	"startColumn": 3,
	"endLineNumber": 34,
	"endColumn": 19
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Property binding ngIf not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the \"@NgModule.declarations\".",
	"source": "ng",
	"startLineNumber": 8,
	"startColumn": 5,
	"endLineNumber": 18,
	"endColumn": 20
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Can't bind to 'ngIf' since it isn't a known property of 'ng-container'.\n1. If 'ngIf' is an Angular directive, then add 'CommonModule' to the '@NgModule.imports' of this component.\n2. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.",
	"source": "ng",
	"startLineNumber": 8,
	"startColumn": 19,
	"endLineNumber": 8,
	"endColumn": 72
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "The pipe 'async' could not be found",
	"source": "ng",
	"startLineNumber": 8,
	"startColumn": 20,
	"endLineNumber": 8,
	"endColumn": 44
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "'mat-tab' is not a known element:\n1. If 'mat-tab' is an Angular component, then verify that it is part of this module.\n2. If 'mat-tab' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.",
	"source": "ng",
	"startLineNumber": 10,
	"startColumn": 7,
	"endLineNumber": 16,
	"endColumn": 17
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Property binding ngIf not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the \"@NgModule.declarations\".",
	"source": "ng",
	"startLineNumber": 10,
	"startColumn": 7,
	"endLineNumber": 16,
	"endColumn": 17
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Can't bind to 'ngIf' since it isn't a known property of 'mat-tab'.\n1. If 'mat-tab' is an Angular component and it has 'ngIf' input, then verify that it is part of this module.\n2. If 'mat-tab' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.\n3. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.",
	"source": "ng",
	"startLineNumber": 10,
	"startColumn": 34,
	"endLineNumber": 10,
	"endColumn": 69
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Property binding ngIf not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the \"@NgModule.declarations\".",
	"source": "ng",
	"startLineNumber": 21,
	"startColumn": 5,
	"endLineNumber": 32,
	"endColumn": 20
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Can't bind to 'ngIf' since it isn't a known property of 'ng-container'.\n1. If 'ngIf' is an Angular directive, then add 'CommonModule' to the '@NgModule.imports' of this component.\n2. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.",
	"source": "ng",
	"startLineNumber": 21,
	"startColumn": 19,
	"endLineNumber": 21,
	"endColumn": 72
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "The pipe 'async' could not be found",
	"source": "ng",
	"startLineNumber": 21,
	"startColumn": 20,
	"endLineNumber": 21,
	"endColumn": 44
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "'mat-tab' is not a known element:\n1. If 'mat-tab' is an Angular component, then verify that it is part of this module.\n2. If 'mat-tab' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.",
	"source": "ng",
	"startLineNumber": 23,
	"startColumn": 7,
	"endLineNumber": 30,
	"endColumn": 17
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Property binding ngIf not used by any directive on an embedded template. Make sure that the property name is spelled correctly and all directives are listed in the \"@NgModule.declarations\".",
	"source": "ng",
	"startLineNumber": 23,
	"startColumn": 7,
	"endLineNumber": 30,
	"endColumn": 17
},{
	"resource": "/c:/Udemy/angular-testing-course/src/app/courses/home/home.component.html",
	"owner": "_generated_diagnostic_collection_name_#3",
	"severity": 8,
	"message": "Can't bind to 'ngIf' since it isn't a known property of 'mat-tab'.\n1. If 'mat-tab' is an Angular component and it has 'ngIf' input, then verify that it is part of this module.\n2. If 'mat-tab' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.\n3. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.",
	"source": "ng",
	"startLineNumber": 23,
	"startColumn": 33,
	"endLineNumber": 23,
	"endColumn": 68
}]