Press and hold the Power button
If prompted, tap Power off
If the power menu appears, tap Power off
If the phone has no Power off option, press and hold the Power button and Volume Up or Volume Down button together
If the screen is frozen, press and hold the Power button for 10 to 30 seconds until the phone turns off
If the phone uses on-screen controls, swipe down for Quick Settings and tap the Power icon, then tap Power off