issue with iPhone

ok. so I have a huge issue. Yeserday someone was helping medowngrade from iOS 16 beta because an app I needed wouldn't open. Lets just say that after 45 minutes, the phone would not turn on again, and it hasn't ever since. however I have seen a light a little bit, but that is because I tried putting the phone into DFU mode. what am I supposed to do?

Which phone is it?

You need to do a full firmware restore through iTunes on PC, not sure of the steps for mac. Also, the screen should be completely black in DFU mode.

What is DFU mode? Just wondering.

In response to Alden. It is an iPhone 11. And in response to George. DFU is short for device firmware update.

and that is what I am trying to do on my PC.

I do not use a mac.

okay thanks for the ansour

Connect the phone to the computer. Press volume up, follow that quickly with a volume down press and then follow that quickly with a side button press. It should take about thirty seconds for the computer to see the phone. You will need iTunes on Windows. When it asks about the phone being in recovery mode, press restore. This does delete all data, but you've already lost it all due to a corrupted OS.

that didn't do anything. do you mean when it is in DFU mode? I will be most likely seeing a family friend who is a tenition tomorrow, so he will get in touch with me about the issue. I already mesaged him on facebook messenger with my computer to let him know about the issue.

A side button hold*
-- (aldenmaster):
Connect the phone to the computer. Press volume up, follow that quickly with a volume down press and then follow that quickly with a side button press. It should take about thirty seconds for the computer to see the phone. You will need iTunes on Windows. When it asks about the phone being in recovery mode, press restore. This does delete all data, but you've already lost it all due to a corrupted OS.

--

that still didn't do anything.