When your phone battery is draining way too fast, everything seems to be running painfully slow, and certain apps keep failing to work as usual, it could be because you have way too many apps running in the background. To force quit or 'kill' an app that is running in the background, simply double tap the home button and swipe up on the things you want to close.
The tip above is something most of us already know about. But were you aware that you can kill up to three apps at once? Instead of sitting there for ages, swiping up for every single open app, you can now speed things up by working in threes. Simply use three fingers when you swipe up and you'll be able to close three apps at a time.