Huge FPS problems on iOS

It’s just so laggy and it gets worse every time I open the app I’ve tried multiple methods but none works I just can’t get it to stop lagging I’ve turned all my graphics down but even yet I can’t stop lagging it’s so buggy that you can’t mine blocks properly and in multiplayer the lag is impossible to support. I don’t know what to do I’ve tried everything I could please fix this issue .