Note: The game can be laggy/glitchy when you perform certain action for the first time, e.g starting extreme trial, opening shop, battle pass etc. This is because the game downloads the patch, extract & cache data during runtime, so it depends on your internet speed as well. Technically after the game downloaded the in-game patch completely then you won't face the issue anymore.
TLDR: when game is stuck/stopped loading, wait for 5-15 seconds, if it still doesn't load then Force Stop the app, and restart.