When you click on the activity button you will see any ‘activity’ from any of the teams you are enrolled in.
It will show any messages from a teacher, a chat group or a teams channel you are a member of.
You can filter any activity to show things like: unread messages, mentions, replies, chats or conversations you are following, reactions to posts you have made. Don’t worry about Apps, Suggested and Trending.
You can also go between the teams feed and your own activity.
It is important that your notifications are switched on so that you don’t miss anything important posted by a teacher.