Starting a new task even if previos doesn't finished yet.

I have a simple file browser which i can open by code below:

 FileBrowser.Instance.ShowDialog(FileBrowserMode.SingleFile, (results) =>
 {
     string path = results[0];
 }

In file browser, at the end of operation i have this code:

 HideDialog();
 OnFinish(Results);

HideDialog():

 public void HideDialog()
 {
     DialogCG.alpha = 0;
     DialogCG.interactable = false;
     DialogCG.blocksRaycasts = false;
 }

OnFinish - this is a callback function which will be called after FileBrowser will finish all work and will hide itself.

Also i have a loading frame. I can make it visible by calling suitable function:

 Notification.Instance.ShowLoadingAlert();

and i can hide it when i want by calling:

 Notification.Instance.HideLoadingAlert(); 

So, my whole code in simple looks like this:

 FileBrowser.Instance.ShowDialog(FileBrowserMode.SingleFile, (results) =>
 {
     string path = results[0];
     Notifications.ShowLoadingNotification();
     var bytes = File.ReadAllBytes(path);
     Notifications.HideLoadingNotification();
     Debug.Log("Image size: " + bytes.Length);
 }

So, in my mind how it should works:

1. FileBrowser hidding itself.

2. FileBrowser calling a callback method and pass a results there.

3. Loading frame must be shown now.

4. Starting to read bytes from file. <= Here we will got a freeze but no problem.

5. After reading file, loading frame must be hidden.

6. And finally we should see a debug message.

And how it really works :

1. FileBrowser calling a callback method and pass a results there.

2. Starting to read bytes from file. <= Here we will got a freeze but no problem.

3. FileBrowser hidding itself.

4. Loading frame visible.

5. Loading frame hidden.

6. Printing a debug message.

Why order was broken and how i can keep it working in order?