loginUser() {
  if(this.username == 'test' && this.password == 'test'){
    this.service.login().subscribe(userIsLoggedIn =>
      this.router.navigate(['admin/overview']));
  }
}

{
  path: 'admin',
  component: AdminLoginComponent,
  data: {title: 'Admin'}
},
{
  path: 'admin/overview',
  component: AdminOverviewComponent,
  canActivate: [AuthGuard],
  data: {title: 'Overview'}
}

@Injectable()
export class AuthService {
  user: Observable<firebase.User>;
  constructor(private firebaseAuth: AngularFireAuth){
    this.user = firebaseAuth.authState;
  }
  isLoggedIn = false;

  login(email: string, password: string): Observable<boolean> {
    this.firebaseAuth
  .auth
  .signInWithEmailAndPassword(email, password)
  .then(value => {
    return Observable.of(true).delay(1000).do(val => this.isLoggedIn = true);
  })
  .catch(err => {
    console.log('Something went wrong:',err.message);
  });
return Observable.of(false).delay(1000).do(val => this.isLoggedIn = false);
}
}

constructor(private router: Router, private service: AuthService){}
loginUser() {
    this.service.login(this.email, this.password).subscribe(userIsLoggedIn =>
      this.router.navigate(['admin/overview']));
      this.email = this.password = '';
      console.log('test');
  }