So in all videos I've seen online people open multitasking by swiping to the middle of the screen, waiting and then the multitasking overview opens. However you can also just swipe up and then immediately to the right, like this: This is much quicker as it always opens (unlike with the waiting) and you don't have to pause. Also, when you want to close an app from memory, just keep it pressed shortly and immediately swipe up. This will close it without having to wait too long. Some might know this already, but I think for many this will be new.