I want to use a Firebase to make Login InterFace But it is crashing

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Firebase.Auth;
using System;

public class FireBaseAuthManager
{
    private static FireBaseAuthManager instance = null;

    public static FireBaseAuthManager Instance
    {
        get
        {
            if (instance == null)
            {
                instance = new FireBaseAuthManager();
            }

            return instance;
        }
    }

    private FirebaseAuth auth; // 로그인의 아이디,비번 정보
    private FirebaseAuth user; // 로그인한 유저 데이터 

    public String UserId => user.UserId;

    public Action<bool> LoginState;


    public void Init()
    {
        auth = FirebaseAuth.DefaultInstance;
        auth.StateChanged += OnChanged;
    }

    private void Onchanged(object sender, EventArgs e)
    {
        if(auth.CurrentUser != user)
        {
            bool signed = (auth.CurrentUser != user && auth.CurrentUser != null);
            if(!signed && user != null)
            {
                Debug.Log("로그아웃");
                LoginState?.Invoke(false);
            }

            user = auth.CurrentUser;
            if (signed)
            {
                Debug.Log("로그인");
                LoginState?.Invoke(true);
            }
                
        }
    }
  

    public void Login(string email, string Password)
    {
        auth.SignInWithEmailAndPasswordAsync(email, Password).ContinueWith(task =>
        {

            if (task.IsCanceled)
            {
                Debug.LogError("로그인 취소");
                return;
            }
            if (task.IsFaulted) // 회원가입 오류 이류:  이메일 오류, 비밀번호 오류 , 이미 가입된 이메일
            {
                Debug.LogError("로그인 실패");
                return;
            }

            AuthResult authResult = task.Result;
            FirebaseUser user = authResult.User;
            Debug.LogError("로그인 완료");

        } );
    }

    public void Create(string email,string Password)
    {
        
        auth.CreateUserWithEmailAndPasswordAsync(email, Password).ContinueWith(task =>
        {
            if (task.IsCanceled)
            {
                Debug.LogError("회원가입취소");
                return;
            }
            if (task.IsFaulted)
            {
                Debug.LogError("회원가입실패");
                return;
            }

            AuthResult authResult = task.Result;
            FirebaseUser user = authResult.User;
            Debug.LogError("회원가입완료");
        });
       
    }

    public void LogOut()
    {
        auth.SignOut();
        Debug.Log("로그아웃");
    }
}

When I Loggin InterFace is succeed it is Okay but when I arrangement the code to optimizer the Scripts
It is Crashed to much
So What Can I do

Please post LoginSystem.cs. It appears as though the errors are there and perhaps related to not referencing FireBaseAuthManager.cs properly.