Using apps builds up data which is stored in a place called the cache. If this builds up it can cause the app to not work properly
In Teams, this can result in a number of symptoms such as Teams crashing, freezing having to be restarted often etc.
To resolve this please follow the below instructions:
1. Sign out on Teams > Quit Microsoft Teams by right clicking the icon and select Quit.
2. On your keyboard, Hold Windows key and Press R - this will open the RUN dialogue box
3. Cut and paste this: %appdata%\Microsoft\Teams in the RUN field then OK.
4. Delete the contents of the entire folder that opens. (you can press Ctrl + A to select everything at once if you like, then press Delete)
5. Restart Device > Restart Microsoft Teams > Sign In.