Similar thing happened to me idk if it's android or the games problem but when I put my max frame rate to 60hz or 90hz in settings, brawlstars gets stuck at like 30hz or less.
When I pull the notification shade down, things get faster because the system refresh rate overrides the game. For some reason the game thinks 60hz is not available and falls to 30hz.
Now when I set max rate to 120hz everything is fine, but I can't save battery at 60hz/90hz anymore. Some games work fine regardless of settings.
Just use something like ente auth, then you can just login online anytime and get your 2fa codes.