AgainTheGame/endTrigger.cs

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

public class endTrigger : MonoBehaviour
{
  private void OnTriggerEnter(Collider other)
  {
    if (other.gameObject.CompareTag("Player"))
    {
      SceneManager.LoadScene("end");
      SceneManager.UnloadSceneAsync("game");
    }
  }
}