iPhone 7 not charging and Bootloop when DFU

I have an iPhone 7 and I am trying to fix it. The iPhone got stuck on a boot loop with the white screen and Apple logo until the battery died. When I tried to charge the phone, the phone did not respond to charging, and I could not do anything to fix it.

Then I bought a new battery, thinking that maybe it could be a battery problem. I have replaced the new battery and the iPhone turn on again but with the same problem, the boot loop.

I tried to connect the iPhone to my Mac and recognizes it. But still not recognized when charging. Now I'm with the iPhone opened, connecting and disconnecting the battery flex connector, in order to not waste the battery, and trying to restore the software with iTunes holding volume down and power button, showing the black screen with a lighting charger and iTunes logo.

The process starts, but when the iPhone is automatically restarted during the process it show the logo, and then the loading bar under the logo 0,5 seconds and the iPhone restarts on showing the black screen with a lighting charger and iTunes logo again. The process fail with error 4013.

I have tried the process with iTunes and Dr.fone and I have the same problem. Any idea? I need to repair it without pay 370$ if possible...

Thank you!