Drag and Drop with instantiate

Hi,

I am a Beginner, and I try to do a Drag an Drop but from a gameObject which is instantiate many times.

Learning from a tutorial I have done this script right below, but if I have just one time the gameObject, it works perfectly, but when I had the instantiate script, I am not able to drag the gameObject after to be dropped the first time.

Thank you in advance for your answer !

script to DragandDrop :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.EventSystems;
 using UnityEngine.UI;
 
 public class WaterDND : MonoBehaviour
 {
   private Vector3 screenPoint;
   private Vector3 offset;
   private Vector3 curPosition;
   private Vector3 otherPosition;
   private Vector3 curScreenPoint;
   private bool dropping = false;
 
     void Start()
     {
 
 Camera cam = gameObject.GetComponent();
     }
 
     void Update(){
       Debug.Log (curPosition + gameObject.name);
       screenPoint = Camera.main.WorldToScreenPoint(gameObject.transform.position);
       curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
       curPosition = Camera.main.ScreenToWorldPoint(curScreenPoint);
     }
 
   void OnMouseDown(){
 screenPoint = Camera.main.WorldToScreenPoint(gameObject.transform.position);
   }
 
   void OnMouseDrag() {
   curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
   curPosition = Camera.main.ScreenToWorldPoint(curScreenPoint);
   transform.position = curPosition;
   }
 
   void OnMouseUp() {
     if(dropping == false) {
     Destroy(gameObject);
         }
     else{
 transform.position = otherPosition;
     }
 
 
   }
 
   void OnTriggerEnter2D(Collider2D other){
 otherPosition = other.transform.position;
 
         if (other.tag == "slot")  {
             dropping = true;
 
                   if (other.name == "Slot AC"){
                     gameObject.transform.eulerAngles = Vector3.forward * 0;
                   }
                   if (other.name == "Slot AD"){
                     gameObject.transform.eulerAngles = Vector3.forward * -45;
                   }
                   if (other.name == "Slot CD"){
                     gameObject.transform.eulerAngles = Vector3.forward * -90;
                   }
                   if (other.name == "Slot ArD"){
                     gameObject.transform.eulerAngles = Vector3.forward * -135;
                   }
                   if (other.name == "Slot AG"){
                     gameObject.transform.eulerAngles = Vector3.forward * 45;
                   }
                   if (other.name == "Slot CG"){
                     gameObject.transform.eulerAngles = Vector3.forward * 90;
                   }
                   if (other.name == "Slot ArG"){
                     gameObject.transform.eulerAngles = Vector3.forward * 135;
                   }
                   if (other.name == "Slot ArC"){
                     gameObject.transform.eulerAngles = Vector3.forward * 180;
                   }
                   if (other.name == "Slot CC"){
                     gameObject.transform.eulerAngles = Vector3.forward * 0;
                   }
 
         }
   }
 
   void OnTriggerExit2D(Collider2D other){
             dropping = false;
             }
 }

Script to Instantiate

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.SceneManagement;
 using UnityEngine.EventSystems;
 
 public class generateGeode : MonoBehaviour
 {
 
 public GameObject myPrefab;
 private bool done = true;
 
 
 void OnMouseDrag(){
 
     if (done == true){
 done = false;
     Instantiate(myPrefab, new Vector3(640,30,0), Quaternion.identity, GameObject.FindGameObjectWithTag("Canvas").transform);
 myPrefab.transform.localScale = new Vector3 (15, 15, 0);
 
     }
 
   }
 }