Issuse with 3d Text Update or couple months thinking about error. How its works?

Hello! I cant slove 1 error with 3d text. I see many YouTube video and for uploaders of video its works, but with my projects its dont work... Here my Update script. i just call that script from another to update text value .

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class PointTracker : MonoBehaviour {
 
      GameObject PointNum;
      Text TextNum;
 
      int CurrentPoints = 0;
 
     // Use this for initialization
     void Start () {
         PointNum = GameObject.Find("PointNum");
         TextNum = PointNum.GetComponent<Text>();
         UpdatePoints(CurrentPoints);
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     public void UpdatePoints(int addNum)
     {
         CurrentPoints = CurrentPoints + addNum;
         TextNum.text = "" + CurrentPoints;
     }
 }

and its string

 TextNum.text = "" + CurrentPoints;

Call that error:

 NullReferenceException: Object reference not set to an instance of an object
 PointTracker.UpdatePoints (Int32 addNum) (at Assets/Scripts/PointTracker.cs:27)

Please help me and say what i am doing wrong... Thanks.