No gameobject instance again in update

Hello, I need handle instantiating of GameObject by ,,MarkInst" and ,,CanMarkInst" bool, but when I hit mouse button 0 these bools go false but it still can instantiate when I am hitting mouse button 0... :/ Please help :)

     using UnityEngine;
     using System.Collections;
     
     public class Smazat : MonoBehaviour {
         public Camera cam;
     
         public GameObject Marker;
     
         public bool MarkInst = true;
         public bool CanMarkInst = true;
     
         public float x;
         public float y;
         public float z;
     
         void Update() {
             if (Input.GetMouseButton(0))
             {
                 RaycastHit info;
                 if (Physics.Raycast(cam.ScreenPointToRay(Input.mousePosition), out info))
                 {
                     x = info.point.x;
                     z = info.point.z;
                     y = info.point.y;
                 }
     
                 if(MarkInst == true && CanMarkInst == true)
                 {
                     Instantiate(Marker, new Vector3(x,y,z), Quaternion.Euler(1,1,1));
                     MarkInst = false;
                     CanMarkInst = false;
                 }
             }
             if (Input.GetMouseButtonUp (0)) {
                 x = 0;
                 z = 0;
                 y = 0;
             }
         }
 }