cant get game to game over

I have a code set so if no enemy is killed within a few seconds the game is over it works at first bit after a few sec0nds it doesn’t , so if you don’t kill a enemy the game wont end. I want it set so that if no enemy is killed after few seconds the game will end but its not

I cant find why … so again it works at first but after a few seconds or a few kills it stops working

What I want= I want throughout the entire game setup so that if no enemy is killed and dragged to top of screen every few seconds the game will end

heres code

using System.Collections;
 
 [RequireComponent(typeof(AudioSource))]
 public class fishdedd : MonoBehaviour {
5. 
     public AudioClip pop1;
     public AudioClip boing;
     AudioSource audio;
 
10. 
          Animator anim;                    //reference to the animator component
 
 
     void Start()
15.         {
         audio = GetComponent<AudioSource>();
             //get reference to the animator component
             anim = GetComponent<Animator> ();
 
20.         }
         void OnCollisionEnter2D(Collision2D other)
          //void OnTriggerEnter2D(Collider2D other) 
     {
         
25. */
 if (other.gameObject.tag == "topy" || other.gameObject.tag == "Wall" ) 
 {
     // do something when we collide with "enemy1" OR "enemy2"
     anim.Play("fishded");
30.     anim.SetTrigger("Die");
     GetComponent<AudioSource> ().Play ();
         audio.PlayOneShot(pop1, 0.7F);
             DeathWatch.ReportDeath ();
             //ScoreManager.score += scoreValue;
35. }
 else if (other.gameObject.tag == "shark" || other.gameObject.tag == "shark" ) 
 {
     // do something else when we collide with "enemy3" OR "enemy4"
             anim.Play("fishded");
40.             anim.SetTrigger("Die");
             GetComponent<AudioSource> ().Play ();
             audio.PlayOneShot(boing, 0.7F);
             DeathWatch.ReportDeath ();
 }
45. 
     }
 }
 
         
50. 
         }
     }
 }
 */

here s deathwatch code below

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class DeathWatch : MonoBehaviour {

	public AudioClip pop1;
	public AudioClip boing;
	AudioSource audio;
	Animator anim;  

		private const float DeathTimeLimit = 33;
		private static float DeathCountdown = DeathTimeLimit;

	void Start()
	{
		audio = GetComponent<AudioSource>();
		//get reference to the animator component
		anim = GetComponent<Animator> ();
	 
	}
		
		    private void Update() {
			DeathCountdown -= Time.deltaTime;
			if (DeathCountdown < 0) {

				GameOver ();
			anim.Play("fishded");
			anim.SetTrigger("Die");
			 
			audio.PlayOneShot(pop1, 0.7F);
				// Game over
			}
			    }
	private void GameOver()
	{
		Application.LoadLevel("Menu");
	}
		public static void ReportDeath() {
			DeathCountdown = DeathTimeLimit;
		}
		 }

without the deathwatch code it is hard to help you, there are functions in the code above that you have not shown the definitions for.