Game manager.cs

using UnityEngine;
using UnityEngine.SceneManagement;

public class GameManager : MonoBehaviour
{
    bool gameHasEnded = false;
    public float restartDelay = 2f;

    public void EndGame()
    {
        if (gameHasEnded == false)
        {
            gameHasEnded = true;
            Debug.Log("Game over");
            Invoke("RestartGame", restartDelay);
        }
    }

    void RestartGame()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().name);
    }
}