Why is my middle and upper part of my phone is not workin

Your question isn't clear; are you saying the touch screen isn't working or the display isn't showing a picture?

Either way, you'll want to try restarting the phone, and as a last resort you could try doing a complete restore back to factory settings - after backing up your data first, of course.

If that doesn't help, then the chances are you'll need to replace the screen to fix the problem. Since the touch screen (digitizer) and the OLED display are fused together into a single unit, replacing the assembly should fix the issue either way. Sorry to say iFixit doesn't have a guide to that repair on your phone, but the Spanish site Nadie Me Llama Gallina has just what you need.

Manuales / Samsung Galaxy A30s / Fullscreen - Nadie Me Llama Gallina

As you might guess, the site is in Spanish, but if you use it with the Chrome browser's translation feature, it becomes quite usable no matter what your native language may be, and their guides are well done and complete.

Good luck and let us know how it all turns out!