I cant restore the iPhone.

Hello,

I want to restore my iPhone because it boot loops and I want to fix this issue. I put it in DFU mode, iTunes recognizes it and begins with the update. Then the phone gets restarted so the update starts and it just boot loops again and I get unknown error (21). Please help.

-Update:

I tried again to restore it and it does nothing it says unknown error (11)

Thanks!