VS isn't working with unity libraries?

Unity Engine
1

So I’m working on a online multiplayer game, but for some reason I can’t get VS to identify everyday unity classes and object:

using System.Collections;
using System.Collections.Generic;
using System.Runtime.Remoting.Channels;
using UnityEngine;
using UnityEngine.UI;
public class UIManager : MonoBehaviour
{
    public static UIManager instance;
    public GameObject startMenu;
    public InputField usernameField;
    private void Awake()
    {
        if (instance == null)
        {
            instance = this;
        }
        else if (instance != null)
        {
            Debug.Log("Instance already exists, destroying instance...");
            Destroy(this);
        }
    }
    public void ConnectToServer()
    {
        startMenu.SetActive(false);
        usernameField.interactable=false;
        Client.instance.ConnectToServer();
    }
}

I dont know if this is happening to anyone else, but the GameObject and InputField, aren’t being assigned properly. Help please.

2

Try the steps here, the most important is #3: