My game freezes after like 20 seconds logging in. Can I delete the app and then reinstall and login with my Facebook account without losing my progress?
If you are connected to Facebook when you reinstall the game you can reconnect to Facebook and recover your account.
Facebook is there to save your account info so you can jump between devices or installs.
I have also noticed slowness since the new notification was introduced. I contacted support and am not seeing slowness with any other game. If it helps, I think random freeze and slowdowns is side effect of this new notification system, maybe it is taking too much memory.