Why is my phone screen not displaying anything.

@ykotunaiya you are not telling us what you have checked. It reads like you are saying the display flex is disconnected. If so, it needs to be reconnected. If your phone behaves like the flex is disconnected, then it is most likely that the screen has failed.

I'd start by replacing the screen. Since iFixit does not yet have a guide for this, use something like this video to replace it. Replacement screen are readily available at many online stores. Purchase one from a vendor that appeals to you.

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.