Option 1- Leave a group using Microsoft Teams
You can leave a team at any time by choosing the team name, and then selecting More options > Leave the team.
You'll receive a confirmation message to make sure that you want to leave the team.
Option 2 - Leave the group from Outlook on the Web
In the left pane, under Groups, select the group you want to leave.
At the top of the message list, select > Settings.
Select Leave group.