Android back button really slow

Hello.

I have an application with multiple scenes.

When I am going forward, i mean loading scene number 1 from number 0, all is well.

But when i try to load a previous scene, it takes a lot of time. How can i make it faster?

 if (Input.GetKeyDown(KeyCode.Escape))
         {
             Application.LoadLevel("PreviousScene");
 
             // ON BACK PRESSED 
         }

I am currently using Input.GetKeyDown in update method.