How Can I Reset Values?(Unity3D)

Hi I"m using using Global,Local codes for show Health, Score and Timer Those showing right values when i start a game but there is a problem when i restart a game I'm using code below, for make a game restart.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 public class MainMenu : MonoBehaviour {
 
     private GlobalInformation gi;
     private int level;
 
     public void PlayGame()
     {
         SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex + 1);
     }
     public void QuitGame()
     {
         Debug.Log("QUIT A GAME");
         Application.Quit();
     }
     public void ReturnGame()
     {
         Application.LoadLevel(0);
      
     }
     
 
 }
 

and I'm using "return Game" for restart game.

Here are my Global and Local codes using UnityEngine; using System.Collections; using UnityEngine.SceneManagement; using UnityEngine.Networking; using UnityEngine.UI;

  public class GlobalInformation : MonoBehaviour {
  
      /* Static reference to GlobalInformation script */
      public static GlobalInformation gi;
      public int globalscore;
      public float timer;
      public int phealth = 100;
      public int maxHealth = 500;
  
      private NetworkStartPosition[] spawnPoints;
  
  
      /* Test global variable */
      public int globalVariable;
  
  
      /* Setter method for changing the global variable */
      public void setHealth(int value) {
          phealth = value;
      }
  
      /*Getter method for retrieving the global variable */
      public int getGlobalVariable() {
          return globalVariable;
      }
  
  
      public void addscore(int value)
      {
          globalscore += value;
      }
  
      public void addtimer(float value)
      {
          timer -= value;
      }
  
      public void adjusthealth(int value)
      {
          phealth += value;
          if (phealth < 0) {
              phealth = 0;
              NextLevelButton(3);
          }
          if (phealth > maxHealth)
              phealth = maxHealth;
  
          if (maxHealth < 1)
              maxHealth = 1;
  
      }
  
  
  
  
      public int getscore()
      {
          return globalscore;
      }
  
      public float getTimer()
      {
          return timer;
      }
  
      public int gethealth()
      {
          return phealth;
      }
  
      public void NextLevelButton(string levelName)
      {
          Debug.Log("index string activated");
  
  
          SceneManager.LoadScene(levelName);
      }
      public void NextLevelButton(int level)
      {
          Debug.Log("index int activated");
  
          if (level == 0)
          {
              Debug.Log("Level zero");
              gi.setHealth(100);
              gi.addtimer(100);
          }
          if (level == 3)
          {
              Debug.Log("Level four");
              gi.setHealth(100);
              gi.addtimer(100);
              SceneManager.LoadScene(4);
          }
  
      }
      
      
      void Awake() {
          /* Sets the first instance of GlobalInformation that is loaded to the static GlobalInformation gi */
          /* Any further instances are immediately destroyed */
          /* Called in Awake() because Awake() runs before Start() */
          if(gi == null) {
              DontDestroyOnLoad(gameObject);
              gi = this;
          } else if(gi != this) {
              Destroy(gameObject);
          }
      }
  }
  
 

and

  using UnityEngine;
  using UnityEngine.SceneManagement;
  using System.Collections;
  
  public class LocalInformation : MonoBehaviour {
  
      /* Reference to GlobalInformation script */
      private GlobalInformation gi;
      
      /* Values used for testing */
  
      public int health; /* Value to change the global variable to; Set through the Inspector */
      private float startTime;
      public int score;
      
      void Start () {
          gi = GlobalInformation.gi; /* Set gi to the static reference of gi in the GlobalInformation script */
          health = gi.gethealth(); /* Set oldTestValue to the current global variable before changing it */
          startTime = (float)gi.getTimer();
          InvokeRepeating("countdown", startTime, 1.0f);
          score = gi.getscore();
      }
      
      void Update() {
          /* Loads scenes on key press of 1, 2 or 3 at the top of the keyboard */
          /* Used to test the changing of the global variable */
          if (Input.GetKeyDown(KeyCode.Alpha1)) {
              SceneManager.LoadScene(0);
          }
          if (Input.GetKeyDown(KeyCode.Alpha2)) {
              SceneManager.LoadScene(1);
          }
          if (Input.GetKeyDown(KeyCode.Alpha3)) {
              SceneManager.LoadScene(2);
          }
          if (health < 0) {
              health = 0;
              gi.setHealth(100);
              gi.addtimer(100);
              gi.NextLevelButton (4);
          }
  
          
      }
      public void countdown()
      {
          gi.addtimer (-1);
      }
  
      void OnGUI() {
          /* Display the old and new global variables */
          GUI.Label(new Rect(10,10,200,30), "Health: " + gi.gethealth());
          GUI.Label(new Rect(10,30,200,30), "Score: " + gi.getscore());
          GUI.Label(new Rect(10,50,200,30), "Timer: " + gi.getTimer());
      }
  
  }

Please tell me what i have to put more info or something else.. Thank you