Disabling the Picture-in-Picture feature on iPad – Here’s how it works
iOS 11: How to Disable the e Picture on Picture on iPad
Follow these few simple steps to permanently turn off the feature introduced in iOS 9 on your iPad:
First, pick up your iPad and then open the Settings app on the Home screen. Then select the menu item "General" from the list on the left side of the screen. Then tap the "Multitasking & Dock" entry on the right.
Now slide the slider to the left next to "Permanent video overlay" to disable the picture-in-picture feature. You can now exit the Settings app.
Disabling "Permanent video overlay" will prevent the video from resuming running down the screen in the future when you press the Home button Activate the function at any time by simply dragging the slider back to the right.