Why is my phone uses itself?

@natinael that is what is called "Ghost Touching" it is most commonly caused by a separation with the digitizer assembly. Sine the LCD and the touchscreen on this model are fused, replacing the complete display assembly should fix this.

Of course you also want to check your software. MAke sure you have everything updated. If nothing else you can try and reset your software. Of course, make sure you have all of your files backed-up.

Since iFixit does not yet have a guide for this, use something like this video Replacement display assemblies are readily available at many online places. Purchase it from a vendor that you trust etc.

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.

Repair is War on Entropy!