Half of my screen cannot be touch

Has your phone experienced any kind of damage recently, such as being dropped or exposed to liquids? Even the act of carrying the phone in your pocket and sitting down can damage the display or the digitizer (touch screen).

Whatever the cause, your digitizer is obviously having issues. By far the most common reason is that signals from the touch screen aren't getting to the ribbon cable that connects it to the phone, and that can almost always be fixed by replacing the screen. Sorry to say iFixit doesn't have a guide to that repair for you, but your question has come up in the past and has been answered here.

SOLVED: How to change the screen? - Galax J8 - iFixit

As you work, take lots of pictures and once you're done you can use them to create your own iFixit guide to that repair. It's easy, fun and will earn the appreciation of the repair community, especially those who come after you with the same problem.

Create a new Guide - iFixit

Good luck, and be sure to let us know how it all turns out!