Why is my phone showing lines

@emmanueloroba it would be great if you can give us more history. Things like you dropped the phone or it got water damaged etc. and what you have checked and tried, are pretty important. Since you did not provide that info, I suggest that this is caused by a bad display.

Since ifixit does not yet have a guide for that, use something like this video to replace the display. It is readily available at many online stores. Just make sure you order one for your version of the phone.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.