Except for admin, any member of a group conversation can leave the group at any time.
To leave a group conversation:
1. On the group page click on Settings on the top right corner.
2. Click on Leave Conversation from the menu.
1. Tap on the hamburger menu icon.
2. Tap on Discussions.
3. Choose the group conversation which you want to leave.
4. Tap on the menu button on the top right corner.
5. Tap on Leave Discussion on the bottom of the screen.
6. Tap on Yes on the pop-up.