Old scene still appears for short time when switching scene

So I have a canvas which doesnt get destroyed because it holds and slider whih shows a progressbar. It also has a button which is interactable when the progress of loading is 0.9.. The problem i am having is when I click the button (see activateNewScene()). Basically what happens is when I click on the button is that i load my scene and my disable my canvas. But the problem is that after I disable my canvas the old scene is still shown for about 0.5 sec and than the new scene is loaded. What I want is that after the canvas gets disabled the new scene should show up. without seeing the old scene for short time. So basically when I click on the button the new scene should appear immideatley

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class SceneLoaderGameObject : MonoBehaviour {
     
     private SceneLoader sl;
     public Canvas cav;
 
     void Start () {
         sl = new SceneLoader ();
         cav.GetComponent<Canvas> ().enabled = false;
         DontDestroyOnLoad (this.gameObject);
         DontDestroyOnLoad (cav.transform.parent);
     }
 
     public void setNewNameAndLoadScene(string name){
 
         if (cav != null) {
             Slider slid = cav.transform.GetChild (1).GetComponent<Slider> ();
             Text tx = cav.transform.GetChild (2).GetComponent<Text> ();
             Button bttn = cav.transform.GetChild (3).GetComponent<Button> ();
 
             sl.setNewScene (name);
             sl.setSliderAndTextToChange (slid, tx);
             bttn.onClick.AddListener (() => activateNewScene ());
             cav.GetComponent<Canvas> ().enabled = true;
             cav.GetComponent<Canvas> ().sortingOrder = 1;
 
             StartCoroutine (sl.LoadAsynchron (name, bttn));
 
         }
 
     }
 
     public void  activateNewScene(){
         sl.AsgetOP().allowSceneActivation=true;
         cav.GetComponent<Canvas> ().sortingOrder = 1;
         cav.GetComponent<Canvas> ().enabled = false;
     }
 
 }