When ever i go full screen on google chrome or any other browser or YouTube app my phone takes me back to the homepage after like 3 seconds in full screen mode , any advice?
Is the software on your phone up to date? Go to Apps > Settings > About device > Software update. Also, let's try a soft reset on the phone. This will end all processes and give the phone a fresh start. To do this, press and hold the 'Power' and 'Volume Down' buttons until the phone restarts.
Let us know how you get on.