Microsoft Office App keep crashing on my iPad Air 4th gen.

Hi! I have iPad Air 4th generation with the latest OS version iOS15, and I am using it for my school lecture notes purposes so I sign in the app with my university email ( for storage in one drive purposes).

I just bought this iPad 3 months ago, everything goes smooth until last few weeks, Office app itself started to crash, so I change to the Power point app , however things are not going fine.

There are a lot of my handwritten notes on the pdf files, so I cant see it clearly even though I export the file to any other app or even not showing well o laptop version.

I have been trying to re-install, or sign out, I've tried all the method that suggested by microsoft forum but all are not working as well.

Is there any solutions to help? cause this app is very important as a student for this pandemic time too!

Thanks in advance.