My bottom screen is not not working what i do please suggest

You can Try and Force ReStart Your iPhone as instructed in this article by Apple ➔ How to Force ReStart your iPhone. If that does not work then -

You are probably experiencing a failing display screen if your entire or part of your display is not responsive to your touches and taps. This is more than likely a hardware related issue and will probably require a display replacement. Have your iPhone examined at the Apple Store or at an Authorized Service Center for further diagnosis and resolution.

Axel F.