Is your iPhone X keep restarting with verticals lines on the screen? This may have happens after a huge drop that may have shattered the screen digitizer or other delicate components inside your iPhone.
If so, here are your options:
Hard reset your iPhone
Press and hold both the power and volume down buttons simultaneously. Slide the Power off option and wait till your switches off completely. To turn on your iPhone, press and hold the power button and wait. Once powered on, if the line is still present, follow the steps below.
Replace your screen
The cheaper option is to replace the screen with a brand new iPhone screen. These are fairly cheap and can be found here. iPhone X Screen replacement
If the problem still persists, it is most likely your motherboard. The GPU part of your motherboard may be faulty. This will require more work by a professional.