Basic Menu in Unity 5.3 problem

Hi,

I'm trying to create a very basic menu with just two buttons (play and exit) and a condition to show the menu again when you press M.

Exit works fine but when I play launch, the menu and it's background doesn't disappear !
I watch different video but no one has this problem. I'm sure int's simple but it's going to make me crazy.

Here my code:

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using UnityEngine.SceneManagement;

public class Canvas : MonoBehaviour {...

Basic Menu in Unity 5.3 problem