Huawei p9 Plus - Unresponsive screen

Hello , i just got this damaged phone, it boots, my PC recognized it (VIE-L09) but tthe screen is black, checked the cables inside, checked for water damage, everything is ok.

right now i tried to connect it to my PC and it kept saying connected, after a few seconds disconnected, connected, disconnected, ~10 seconds time between connect>disconnect and the phone was vibrating each time it was connecting/disconnecting. i think it's bootlooping...

I don t know much about this phone, the guy who sold me said "it died in my hand", he had no reason to lie to me, it was really cheap, i don't care if the display is broken, i will buy a new one but i'm asking you guys, where is the problem and how can i solve it?