Issues with Xbox Log in

I'm trying to play on Minecraft (using my Xbox Live account) and I keep having to delete the app and re-download the app: It will not let me fully access my worlds on my Microsoft account. Whenever I try to reload the app, it keeps freezing forcing me to delete the app and re-download to then find I have the same problem of not being able to access anything on my Xbox Live Account. I tried this on another iOS Device and faced the same issues.