@Indr@@@@@123 I can't answer the first part of your question, but you should at least be able to turn off the notifications:
Long press the app icon -> App info -> Notifications -> disable the notifications you don't need/want.
If I were to hazard a guess, I'd say that it's nothing to worry about. You can always try logging in and out of the app, or uninstall then reinstall, and see if that makes the notifications go away. Might be a sync issue.