For starts run
npm install
npm install --save @ckeditor/ckeditor5-angular
npm install --save @ckeditor/ckeditor5-build-classic
npm install --save @ckeditor/ckeditor5-core @ckeditor/ckeditor5-engine @ckeditor/ckeditor5-utils @ckeditor/ckeditor5-watchdog
After go to ckeditor5 and run
npm install
npm run build
To run frontend
npm install
ng serve
To run backend StartApplication