How to Completely Close iPhone Apps
After minimizing an iPhone app, the app continues running in the background, allowing you to recall your session right where you left off by reopening it. The feature comes in handy when you must use several apps simultaneously. The feature, however, can slow down your iPhone if you do not know how to fully close apps. Use the device's hidden app menu to close unwanted apps, speeding up your iPhone.
Double-click the Home key. A list of recently used apps appears.
Swipe the recently used apps list to cycle through your apps.
Hold your finger down on the app you wish to completely close. All apps start wiggling.
Touch the "-" icon on the app you wish to completely close. The app completely closes.