Script work in editor but not in build

Hi, i have problem with my script. It's working in Editor but when i restart Unity or build game it stops working (like it's doesn't exist).

Here's my script:

 using UnityEngine;
 using System.Collections;
 
 public class Leveling : MonoBehaviour {
 
     public Texture2D Exp;
     public Texture2D Background;
 
     public int actLevel = 0;
 
     public int actExp = 0;
     public int[] expToNextLevel;
 
     public string[] addons;
 
     public GUIStyle style;
 
     public void gainExp(int exp)
     {
         actExp += exp;
     }
 
     IEnumerator Wait(float time)
     {
         yield return new WaitForSeconds(time);
     }
 
     void Update()
     {
         if (actLevel >= expToNextLevel.Length - 2)
         {
             actLevel = expToNextLevel.Length - 2;
         }
         if (actLevel >= expToNextLevel.Length - 1)
         {
             actExp = 0;
         }
 
         if (actExp >= expToNextLevel[actLevel + 1])
         {
             actLevel += 1;
             actExp = 0;
             
         }
     }
 
     void OnGUI()
     {
         float exPerc = 0;
         exPerc = (float.Parse("" + actExp) / float.Parse("" + expToNextLevel[actLevel + 1])) * 100;
         GUI.DrawTexture(new Rect(5, Screen.height - 25, 100, 10), Background);
 
         GUI.BeginGroup(new Rect(5, Screen.height - 25, exPerc, 10));
         GUI.DrawTexture(new Rect(0, 0, 200, 10), Exp);
         GUI.EndGroup();
 
         GUI.Label(new Rect(105, Screen.height - 30, 1000, 1000), "" + actLevel, style);
     }
 }