hi i need your help...

i’m a new to programming and i’m creating this game and when i tested it on IOS it display the interstitial ads but does not stop the game in the background . how can i modify this code to do that ?
" this is Ad Manager for Admob "

public class AdManager : MonoBehaviour
{
    public static AdManager Instance { set; get; }
    public string topBannerId;
    public string VideoId;

    private void Start()
    {
        Instance = this;
        DontDestroyOnLoad(gameObject);

        Admob.Instance().initAdmob(topBannerId,VideoId);
        Admob.Instance().loadInterstitial();
       

    }
    public void ShowBanner()
    {
        Admob.Instance().showBannerRelative(AdSize.Banner, AdPosition.TOP_CENTER, 0);
    }
    public void ShowVideo()
    {
        if (Admob.Instance().isInterstitialReady())
        {
            Admob.Instance().showInterstitial();
              
        }
    }
}

public class AdManager : MonoBehaviour
{
public static AdManager Instance { set; get; }
public string topBannerId;
public string VideoId;

 private void Start()
 {
     Instance = this;
     DontDestroyOnLoad(gameObject);

     Admob.Instance().initAdmob(topBannerId,VideoId);
     Admob.Instance().loadInterstitial();
    

 }
 public void ShowBanner()
 {
     Admob.Instance().showBannerRelative(AdSize.Banner, AdPosition.TOP_CENTER, 0);
 }
 public void ShowVideo()
 {
     if (Admob.Instance().isInterstitialReady())
     {
         Admob.Instance().showInterstitial();
         //When you enter the ad it pauses
         Time.timeScale = 0;
     }else{
         //When you exit the ad it resumes back to normal time
         Time.timeScale = 1;
     }
 }

}