NullInjectorError: No provider for InjectionToken angularfire2.app.options

I'm trying to insert the form data in cloud Firestore database. Below is my x.component.ts file in which I'm getting error at constructor where I'm writing

private firestore: AngularFireStore

    import { Component, OnInit } from '@angular/core';
    import { GroupService } from '../shared/group.service';
    import { NgForm } from '@angular/forms';
    // import { NullTemplateVisitor } from '@angular/compiler';
    import { AngularFirestore } from '@angular/fire/firestore';
    // import { AngularFireModule } from 'angularfire2';
    // import { AngularFirestoreModule } from 'angularfire2/firestore';
    
    @Component({
      selector: 'app-group',
      templateUrl: './group.component.html',
      styleUrls: ['./group.component.css']
    })
    export class GroupComponent implements OnInit {
    
      constructor(private groupService: GroupService, private firestore: AngularFirestore) { }
    
      ngOnInit() {
        this.resetForm();
      }
    
      resetForm(form ?: NgForm){
        if(form!= null)
          form.resetForm();
        this.groupService.formData = {
          $key : null,
          firstname: '',
          lastname: '',
          age: null
        }
      }
    
      onSubmit(form : NgForm){
        let data = form.value;
        // this.firestore.collection('groups').add(data);
        this.resetForm(form);
      }
    
    }

The error I get is as below.

ERROR Error: StaticInjectorError(AppModule)[AngularFirestore -> InjectionToken angularfire2.app.options]: StaticInjectorError(Platform: core)[AngularFirestore -> InjectionToken angularfire2.app.options]: NullInjectorError: No provider for InjectionToken angularfire2.app.options! at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:8895) at resolveToken (core.js:9140) at tryResolveToken (core.js:9084) at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8981) at resolveToken (core.js:9140) at tryResolveToken (core.js:9084) at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:8981) at resolveNgModuleDep (core.js:21217) at _createClass (core.js:21270) at _createProviderInstance (core.js:21234)

I had followed the links below but no luck.

Angular Fire Issue 1706

Angular Fire Issue 1416

No provider for InjectionToken angularfire2.app.options

Below is my app.module.ts file.

    import { BrowserModule } from '@angular/platform-browser';
    import { NgModule } from '@angular/core';
    import { AppComponent } from './app.component';
    import { environment } from '../environments/environment'
    import { AngularFireModule } from 'angularfire2';
    import { AngularFireDatabaseModule } from 'angularfire2/database';
    import { AngularFirestoreModule, AngularFirestore } from '@angular/fire/firestore';
    import { GroupsComponent } from './groups/groups.component';
    import { GroupComponent } from './groups/group/group.component';
    import { GroupListComponent } from './groups/group-list/group-list.component'
    import { GroupService } from './groups/shared/group.service';
    import { FormsModule } from '@angular/forms'
    
    
    @NgModule({
      declarations: [
        AppComponent,
        GroupsComponent,
        GroupComponent,
        GroupListComponent
      ],
      imports: [
        BrowserModule,
        AngularFirestoreModule,
        AngularFireDatabaseModule,
        AngularFireModule.initializeApp(environment.firebaseConfig),
        FormsModule
      ],
      providers: [AngularFirestore, GroupService],
      bootstrap: [AppComponent]
    })
    export class AppModule { }

I think I know the answer which solved my problem. I just had to import the below statement to the service I created and need to create object in constructor of service.

import { AngularFirestore } from '@angular/fire/firestore';