Game over Screen and Pause game Screen

hi guys i want to create a really basic game over and pause screen and i don’t have a clue on how to start it can someone help me?
the game over screen it’s for when the character die, and if it’s possible a mission complete screen when i walk in a certain spot/place

using this script for player’s health

using UnityEngine;
using System.Collections;

public class PlayerHealth : MonoBehaviour {
public int MaxHealth = 100 ;
public int CurHealth = 100;
public Texture2D lifebar;
public Texture2D lifebar2;

public float HealthBarLenght;


// Use this for initialization
void Start () {
	HealthBarLenght = Screen.width / 4;

}

// Update is called once per frame
void Update () {
AdjustCurrentHealth(0);

}

void OnGUI() { 
	
GUI.DrawTexture(new Rect(10, 15, HealthBarLenght, 20), lifebar);		
GUI.Box(new Rect(10, 15, HealthBarLenght, 20), CurHealth + "/" + MaxHealth);
GUI.Box(new Rect(10, 15, 300, 20), lifebar2);

	}

public void AdjustCurrentHealth(int adj) {
CurHealth += adj;
	
	if(CurHealth < 0)
		CurHealth = 0;
	
	if(CurHealth > MaxHealth)
		CurHealth = MaxHealth;
	
	if(MaxHealth < 1 )
		MaxHealth = 1;
	
	HealthBarLenght = (Screen.width / 4) * (CurHealth / (float)MaxHealth);
	
	}

}

Usually with a Pause Game you can use this;

bool paused = false;

    void Update()
{
    if (Input.GetKeyDown(KeyCode.Escape))
        togglePause();
}

void togglePause()
{
    if (paused)
    {
        Time.timeScale = 1f;
        paused = false;
    }
    else
    {
        Time.timeScale = 0f;
        paused = true;

    }
}

}

Then you’d have to hook it up to an event if you want to have a menu screens and whatnot