Why my game's FPS drop every time I change scene (Android Game) ?

Hello,
I have a very weird problem. Every time I load my game on my android phone it seems to work greak with 54 to 56 FPS. But when I am loading another scene and return back to my previous scene the FPS drop to 38 - 40. My game has a mane scene where is the game paused and when I press the screen the game starts. That’s my starting screen, but when I load another scene and return back I get this problem.
Moreover all gameobjects reset when I am changing scene I am not keeping anything with DontDestroyOnLoad().
Any idia what may cause this?

Ok, I fixed it. The problem was that every time a scene was loaded a banner ad was created but the banner was never destroyed.