Property 'user' does not exist on type 'void'.ts(2339)

Question

I am trying to create singup form with firebase i am following this video and now i have this error i dont know what is problem and how to fix it

This is my auth.service.ts file

import { Injectable } from '@angular/core';
import { Router } from '@angular/router';
import { GoogleAuthProvider } from 'firebase/auth';
import { AngularFirestore, AngularFirestoreDocument } from '@angular/fire/compat/firestore';
import { AngularFireAuth } from '@angular/fire/compat/auth';
import { Observable, of } from 'rxjs';
import { switchMap } from 'rxjs/operators';
import { user } from './user.models';


@Injectable({
  providedIn: 'root'
})
export class AuthService {
  user$: Observable<user  | null | undefined>;

  constructor(
    private afauth: AngularFireAuth,
    private router: Router,
    private afs: AngularFirestore
  ) {
    this.user$ = this.afauth.authState.pipe(
      switchMap(user => {
        if(user){
          return this.afs.doc<user>('users/${user.uid}').valueChanges()
        }else{
          return of(null)
        }
      })
    );
   }

   async googleSignin(){
     const provider = new GoogleAuthProvider()
     const credential = await this.afauth.signInWithRedirect(provider)
     return this.updateUserData(credential.user); // ERROR IS HERE
   }

   updateUserData(user: any){
     const userRef: AngularFirestoreDocument<user> = this.afs.doc('users/${user.uid}');

     const data = {
       uid: user.uid,
       email: user.email,
       displayName: user.displayName,
       name: user.name
     };

     return userRef.set(data, {merge: true})

   }

   async signOut(){
     await this.afauth.signOut()
     return this.router.navigate(['/']);
   }
}

I am using latest angular and firebase with node I really dont know about this method i use functions.