To change your status, click on your profile picture at the top of the app and set yourself as Available, Busy, Do not disturb, or Away. If you've been idle for five minutes or more, Teams will automatically change your status from Available to Away.
You can also update your status from the command box at the top of Teams. Type /away, /busy, /dnd, or /available to set your status as Away, Busy, Do not disturb, or Available.
There's currently no way to change the amount of time it takes for you to appear as Away. There's also no way to keep yourself Available without being active on Teams.
To change your status, tap More . Then, tap your status to view your options.