I noticed that I have a drop in FPS on my mobile

I have a drop in FPS on my mobile. When I enter on MENU, FPS is down between 55 to 40, but when I enter the world fps drop between 25 to 16 or less, and chunk slowly bear , when fps drops all entity near player , they don' have sounds , like when i hit them they don't have sounds of hitting For a certain period (goat,cow,ect) or when mining