To leave a Super Group, open the Super Group groups tab by swiping left or by taping the # button located in the top right corner of any subgroup chat. Tap the Settings icon in the top right. Scroll to the bottom of Super Group Info and tap "Leave this Super Group" to leave.
Leaving a Super Group will remove you from every subgroup in that Super Group. If you do not want to leave some of the subgroups you are in, you can mute or leave the subgroups you no longer want to be a member of and remain in the Super Group.