ERROR in node_modules/rxjs/Observable.d.ts(1,15): error TS2307: Cannot find module 'rxjs-compat/Observable'.
node_modules/rxjs/Subject.d.ts(1,15): error TS2307: Cannot find module 'rxjs-compat/Subject'.
node_modules/rxjs/Subscription.d.ts(1,15): error TS2307: Cannot find module 'rxjs-compat/Subscription'.
src/app/typescripts/free/dropdown/dropdown-toggle.directive.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/free/dropdown/dropdown.directive.ts(3,12): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/free/dropdown/dropdown.directive.ts(158,9): error TS2339: Property 'filter' does not exist on type 'EventEmitter<boolean>'.
src/app/typescripts/free/navbars/navbar.component.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/free/navbars/navbar.service.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Subject"' has no exported member 'Subject'.
src/app/typescripts/free/navbars/navbar.service.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/alerts/toast/toast.component.ts(18,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/pro/alerts/toast/toast.config.ts(4,10): error TS2305: Module '"/node_modules/rxjs/Subject"' has no exported member 'Subject'.
src/app/typescripts/pro/alerts/toast/toast.config.ts(5,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/alerts/toast/toast.injector.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/alerts/toast/toast.injector.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Subject"' has no exported member 'Subject'.
src/app/typescripts/pro/alerts/toast/toast.service.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/directives/input.directive.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/directives/input.directive.ts(4,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/pro/autocomplete/directives/list-context.directive.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/directives/list-context.directive.ts(4,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/pro/autocomplete/services/base-data.service.ts(1,10): error TS2305: Module '"/node_modules/rxjs/Subject"' has no exported member 'Subject'.
src/app/typescripts/pro/autocomplete/services/completer-data.service.ts(1,9): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/services/completer.service.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/services/local-data.service.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/autocomplete/services/local-data.service.ts(39,12): error TS2339: Property 'next' does not exist on type 'LocalData'.
src/app/typescripts/pro/autocomplete/services/remote-data.service.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/pro/autocomplete/services/remote-data.service.ts(71,8): error TS2339: Property 'map' does not exist on type 'Observable<Response>'.
src/app/typescripts/pro/autocomplete/services/remote-data.service.ts(79,14): error TS2339: Property 'next' does not exist on type 'RemoteData'.
src/app/typescripts/pro/autocomplete/services/remote-data.service.ts(83,14): error TS2339: Property 'error' does not exist on type 'RemoteData'.
src/app/typescripts/pro/file-input/classes/mdb-uploader.class.ts(2,10): error TS2305: Module '"/node_modules/rxjs/Observable"' has no exported member 'Observable'.
src/app/typescripts/pro/file-input/classes/mdb-uploader.class.ts(3,10): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.
src/app/typescripts/pro/smoothscroll/mdb-page-scroll.directive.ts(21,9): error TS2305: Module '"/node_modules/rxjs/Subscription"' has no exported member 'Subscription'.

This happens while just starting the application. 
MDB is not such lightweight to not mind about it dependencies.

But why the hell you're using rxjs-compat and saying that it's angular 6 ready? This errors saying more then clearly: MDB is not even close for being ready to Angular 6.
This time, while my team starting new version of pretty popular web-resource we will not use MDB, because it's cheating with their clients. 

I will check this MDB later if it's really ready to Angular 6, for using it (maybe) in future projects.