Pausing the game after player gets destroyed

Hey guys, as the title says, I want to make it so that when the player game object gets destroyed, the game will then pause and bring up a screen (I've made one called GameOverScreen), however, I cannot seem to get my head around it. Here is my code: using UnityEngine; using UnityEngine.UI;

 public class PlayerHealth : MonoBehaviour
 {
     public float m_StartingHealth = 100f;               // The amount of health each tank starts with.
     public Slider m_Slider;                             // The slider to represent how much health the tank currently has.
     public Image m_FillImage;                           // The image component of the slider.
     public Color m_FullHealthColor = Color.green;       // The color the health bar will be when on full health.
     public Color m_ZeroHealthColor = Color.red;         // The color the health bar will be when on no health.
     public GameObject m_ExplosionPrefab;                // A prefab that will be instantiated in Awake, then used whenever the tank dies.
     public Camera mainCamera;
     public Camera gameOverCamera;
     public GameObject GameOverMenu;
 
     private bool gameover = false;
     private AudioSource m_ExplosionAudio;               // The audio source to play when the tank explodes.
     private ParticleSystem m_ExplosionParticles;        // The particle system the will play when the tank is destroyed.
     private float m_CurrentHealth;                      // How much health the tank currently has.
     private bool m_Dead;                                // Has the tank been reduced beyond zero health yet?
 
     void Start()
     {
         GameOverMenu.SetActive(false);
     }
 
     private void Awake()
     {
         // Instantiate the explosion prefab and get a reference to the particle system on it.
         m_ExplosionParticles = Instantiate(m_ExplosionPrefab).GetComponent<ParticleSystem>();
 
         // Get a reference to the audio source on the instantiated prefab.
         m_ExplosionAudio = m_ExplosionParticles.GetComponent<AudioSource>();
 
         // Disable the prefab so it can be activated when it's required.
         m_ExplosionParticles.gameObject.SetActive(false);
     }
 
 
     private void OnEnable()
     {
         // When the tank is enabled, reset the tank's health and whether or not it's dead.
         m_CurrentHealth = m_StartingHealth;
         m_Dead = false;
 
         // Update the health slider's value and color.
         SetHealthUI();
     }
 
 
     public void TakeDamage(float amount)
     {
         // Reduce current health by the amount of damage done.
         m_CurrentHealth -= amount;
 
         // Change the UI elements appropriately.
         SetHealthUI();
 
         // If the current health is at or below zero and it has not yet been registered, call OnDeath.
         if (m_CurrentHealth <= 0f && !m_Dead)
         {
             OnDeath();
             mainCamera.transform.parent = null;
             mainCamera.enabled = true;
             gameOverCamera.enabled = false;
 
             if (m_CurrentHealth <= 0f && !m_Dead)
             {
                 gameover = !gameover;
             }
             gameover = !gameover;
 
             if (gameover)
             {
                 GameOverMenu.SetActive(true);
                 Time.timeScale = 0;
             }
 
             if (!gameover)
             {
                 GameOverMenu.SetActive(false);
                 Time.timeScale = 1;
             }
         }
     }
 
 
     private void SetHealthUI()
     {
         // Set the slider's value appropriately.
         m_Slider.value = m_CurrentHealth;
 
         // Interpolate the color of the bar between the choosen colours based on the current percentage of the starting health.
         m_FillImage.color = Color.Lerp(m_ZeroHealthColor, m_FullHealthColor, m_CurrentHealth / m_StartingHealth);
     }
 
 
     private void OnDeath()
     {
         // Set the flag so that this function is only called once.
         m_Dead = true;
 
         // Move the instantiated explosion prefab to the tank's position and turn it on.
         m_ExplosionParticles.transform.position = transform.position;
         m_ExplosionParticles.gameObject.SetActive(true);
 
         // Play the particle system of the tank exploding.
         m_ExplosionParticles.Play();
 
         // Play the tank explosion sound effect.
         m_ExplosionAudio.Play();
 
         // Turn the tank off.
         gameObject.SetActive(false);
     }
 }