Issues with my loading screen

Problem: users want to see a visual feedback of the loading progress.

Solution: Display a percentage somewhere on the screen to display a visual feedback

Bug: My loading screen stays at 0% then it shows 90% and then it loads level 1.

Desired output: display 1%..2%...3% so on and so forth

Here is my code:

 IEnumerator WaitForLevelToLoad(GameObject obj)
     {
         yield return new WaitForSeconds(0.001f);
         Destroy(_startWindowInstance);
         var instance = Instantiate(loadGamePrefab);
         instance.transform.SetParent(transform, false);
         yield return new WaitForSeconds(1f);
         AsyncOperation level = SceneManager.LoadSceneAsync("Level1", LoadSceneMode.Single);
         
         var percentage = 0f;
         
         while (!level.isDone)
         {
             yield return null;
             percentage = level.progress * 100f;
             instance.transform.FindChild("PercentValue").GetComponent<Text>().text = percentage.ToString();
         }
     }

I call this coroutine in a function called OnButtonClicked()