Can't click on a button; nothing happens when clicking

Hi Guys,

I have a Problem with the buttons. I'm currently working with Unity 5.3.1.f1. So I have a Panel in a Canvas in which I have buttons (named 1-4).

As you can see on one of the Buttons I have added a function of a script, which should change from Pause to the game so I can play on (Button 1/"SPIEL FORTSEZTEN" in Pic #1). The function used is the last one in the following sript. I even added a little Animation which should make it bigger when it's highlighted, but neither I can resume the Gameplay nor is there an Animation when I get over the button with my mouse.

"PauseManager" is an empty GameObject onto which the script "Pause" is attached. "HudCanavas" is a Canvas. (obviously) "Panel" is a Panel. (no Shit Sherlock) 1/2/3/4 are buttons.

(Sorry for any mistakes as I'm not a native speaker)

 using UnityEngine;
 using System.Collections;
 using UnityEngine.SceneManagement;
 using System;
 using UnityEngine.EventSystems;
 
 public class Pause : MonoBehaviour
 {
 
     public GameObject panel;
     public bool isPaused;
     
 
     void Start()
     {
         isPaused = false;
     }
 
 
 
     void Update()
     {
         if(isPaused)
         {
             GamePause(true);
         }
         else
         {
             GamePause(false);
         }
 
         if(Input.GetKeyDown (KeyCode.Escape))
         {
             SwitchPause();
         }
     }
 
 
 
     void GamePause(bool state)
     {
         if(state)
         {
             Time.timeScale = 0.0f; //Pause 
 
         }
         else
         {
             Time.timeScale = 1.0f; //Pause zuende
         }
 
         panel.SetActive(state);
     }
 
 
 
     public void SwitchPause()
     {
         if(isPaused)
         {
             isPaused = false;
             panel.SetActive(false);
             Debug.Log("YEEEEEEEEAAAAAAAAH");
         }
         else
         {
             isPaused = true;
         }
     }
 
 
 }