error implementing admob ads

i implemented admob ads and everything works fine banner and video ads show just fine , the problem is the reward that the player has to take isn't connected to the ad itself , but the button the player press to watch the ad , i tried showing a panel to notify player that he won a reward after watching the ad but nothing shows , the player just receives the reward and the ad has nothing to do with it , i followed tutorials on youtube exactly , their code worked fine but mine doesn(t work evern though i did exactly the same .........so i chacked my code in visual studio and there was these errors : -code sample : void Start() {

         MobileAds.Initialize(APP_ID);
         this.RewardvideoAD = RewardBasedVideoAd.Instance;
         this.RequestBanner();
         this.RequestRewardBasedVideoAd();
         ShowBannerAd();
         Debug.Log("banner ad on display ");
 
         //----------------------------------------------------------Video AD Subscription 
 
         // Called when an ad request has successfully loaded.
         this.RewardvideoAD.OnAdLoaded += HandleRewardedAdLoaded;
 
         // Called when an ad request failed to load.
         this.RewardvideoAD.OnAdFailedToLoad += 
          HandleRewardedAdFailedToLoad;
 
         // Called when an ad is shown.
         this.RewardvideoAD.OnAdOpening += HandleRewardedAdOpening;
 
         // Called when an ad request failed to show.
         this.RewardvideoAD.OnAdFailedToShow += HandleRewardedAdFailedToShow;
 
       // Called when the user should be rewarded for interacting with the ad.
         this.RewardvideoAD.OnUserEarnedReward += HandleUserEarnedReward;
 
         // Called when the ad is closed.
         this.RewardvideoAD.OnAdClosed += HandleRewardedAdClosed;
     }

errors :

onfailedtoload has redline all over , and two red lines under OnFailedToShow and OnUserEarnedReward , so generated a field for them on visual studio but still the same , any ideas ?thank you