GreedyGameAds.Instance.LoadInterstitialAd("SDK X Interstitial adUnit");

//TO check if Interstitial is loaded
GreedyGameAds.Instance.interstitialAd.IsLoaded

using UnityEngine;
using GreedyGame;

  public class GreedyGameAdsDemoScript : MonoBehaviour
  {

       private void Start()
       {
            //after Initialize the GreedygameAds sdk
            this.LoadInterstitial(); 
       }

       public void LoadInterstitial()
       {
           GreedyGameAds.Instance.LoadInterstitialAd("SDK X Interstitial adUnit");
       }

   }

GreedyGameAds.Instance.ShowInterstitialAd();

 public void GameOver()
  {
        . . .
        . . .        
        this.ShowInterstitial();
  }          
 
  //After Interstitial Method loaded
  public void ShowInterstitial()
  {
      GreedyGameAds.Instance.ShowInterstitialAd(); 
  }

To further customize the behavior of your ad, you can hook into a number of events in the ad's lifecycle: loading, opening, closing, and so on. Listen for these events by registering a delegate for the appropriate EventHandler, as shown below

GreedyGameAds.Instance.interstitialAd.OnAdLoaded
GreedyGameAds.Instance.interstitialAd.OnAdFailedToLoad
GreedyGameAds.Instance.interstitialAd.OnAdOpened
GreedyGameAds.Instance.interstitialAd.OnAdClosed
GreedyGameAds.Instance.interstitialAd.OnAdShowFailed

  public void LoadInterstitial()
  {

       GreedyGameAds.Instance.LoadInterstitial("SDK X Interstitial adUnit");  

       // Called when an ad request has successfully loaded.
       GreedyGameAds.Instance.interstitialAd.OnAdloaded += this.HandleOnAdLoaded;

       // Called when an ad request failed to load.
       GreedyGameAds.Instance.interstitialAd.OnAdFailedToLoad= this.HandleOnAdFailedToLoad;

       // Called when an ad is clicked.
       GreedyGameAds.Instance.interstitialAd..OnAdOpened+= this.HandleOnAdOpened;

       // Called when the user returned from the app after an ad click.
       GreedyGameAds.Instance.interstitialAd.OnAdClosed += this.HandleOnAdClosed;

       // Called when the ad Failed to show
       GreedyGameAds.Instance.interstitialAd.OnAdShowFailed += this.HandleOnAdShowFailed;

   }


  public void HandleOnAdLoaded()
  {
      MonoBehaviour.print("HandleAdLoaded event received");
  }

  public void HandleOnAdFailedToLoad(string error)
  {
      MonoBehaviour.print("HandleFailedToLoadAd event received with message: " +error);                           
  }

  public void HandleOnAdOpened()
  {
      MonoBehaviour.print("HandleAdOpened event received");
  }

  public void HandleOnAdClosed()
  {
      MonoBehaviour.print("HandleAdClosed event received");
  }

  public void HandleOnAdShowFailed()
  {
      MonoBehaviour.print("HandleAdShowFailed event received");
  }