Why is there a green line on my iPhone?
What is the reason for the green line appearing on my iPhone screen?
[Re-Titled by Moderator]
iPhone X
Almost always this is a hardware failure, hopefully just the screen
How to arrange a repair
First try a Forced restart Force restart iPhone – Apple Support (UK)
If no better you should arrange a repair
iPhone Service & Repair - Apple Support
Or
Contact - Official Apple Support
Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"
See also: Get your iPhone, iPad, or iPod touch ready for service - Apple Support