//EXAMPLE 1

    public onSignup(): void {
    this.authService.signupUser(this.signupForm.value)
        .then(response => {
            let userObject = {
                uid: response.auth.uid,
                email: response.auth.email
            };

            setTimeout(() => this.authService.saveNewUserInDatabase(userObject) , 5000)})
        .then(() => {
                setTimeout(() => { this.router.navigate(['/map'])}, 1500);
        })
        .catch(error => {
            console.log(error);
        });
    }

//EXAMPLE 2

public onSignup(): void {
    this.authService.signupUser(this.signupForm.value)
        .then(response => {
            let userObject = {
                uid: response.auth.uid,
                email: response.auth.email
            };

            setTimeout(() => this.authService.saveNewUserInDatabase(userObject)
                .then(() => {
                        setTimeout(() => { this.router.navigate(['/map'])}, 1500);
                    }
                ), 5000)
        })
        .catch(error => {
             console.log(error)
        });
}

public signupUser(user: UserLogin): firebase.Promise<FirebaseAuthState> {
    return this.af.auth.createUser({email : user.email, password: user.password});
}

public saveNewUserInDatabase(user): firebase.database.ThenableReference {
    return firebase.database().ref().child("users").push(user);
}

.then()
.then()