Can't Update/ Restore iPhone 5S

After briefly using my iPhone 5S earlier today, I decided to put it on charge when it was around 25% battery. Later after letting it charge I noticed that it was on the boot screen, as if it had restarted. I left it for a little bit to see if it would actually boot up, but it was clear that the phone was frozen. I decided to manually restart it by using the power button + home button, but after that the phone would just constantly restart over and over without any input from me. Upon further inspection the screen was slightly flickering and had a feint oval ring pattern around the apple logo.

I had a similar experience not too long along, so I thought I could fix it in a similar. I got the phone on the iTunes recovery page and proceeded to plug it into my PC. After downloading the most recent iOS version through iTunes (which is also up-to-date) I attempted to update the phone. However, the phone failed to update and gave me Error 21. After trying a couple more times, and also attempting the restore option which also gave back Error 21, I tried out some common fixes to Error 21.

After trying a few things with no result, I ended up replacing my hosts files since I'm on a PC. And it actually worked!... For a whole 15 seconds before a got a completely new error, that being Error 9 which relates to USB connectivity issues. So this time I tried to get passed this new error by taking out other USBs and switching up which port I used, I also switched my SIM card from my main device to this one just in case. And after trying to update it again multiple times, I kept getting Error 21 again, and no matter what I do I can't bypass it, not matter what USB port I using, what I do to my host files, with or without the SIM card, etc.

Which brings me here. After doing this for a very long frustrating hour, I decided to seek community help. If anyone can help me fix this issue as well as prevent me from throwing the Phone in the microwave as a last resort, I would be grateful.

Thanks in advance.