Need PC/Internet help!

Hello,
so one massive problem appeared for me today.
For like a year at home we've got a connection from UPC with their modem (technicolor tc7200 I think, it's a modem-router I believe and UPC doesn't allow you to use anything else but that shit..).
So as I've said we got it for like a year or so and we had two ethernet cables in use, my brothers' PC and mine + we obviously used our phones, ipad and two ntbs on WiFi sometimes, there were never issues with our PCs, only the WiFi on notebooks was sometimes laggy and it took 5mins to catch up..

But like two weeks ago we got a 3rd cable for one of the laptops and since then the internet is going full retard, the wifi is okay and fine. But the internet on PCs and laptop just sometimes goes off and it takes a few minutes to get back to normal..
But yesterday I unplugged my cable from the PC (let the PC stay on all night) and plugged it in my ntb which I'Ve done a few times before already, but when I tried to plug the cable back into PC today, it just won't work, restarted PC many times, tried to use sme DNS settings and bringing it back to normal but nothing helped, still there is the little shit yellow triangle and it won't work..

I've tried the troubleshooting shit through network sharing centre and this is what I've got from it -


also this is what it shows when the cable is plugged in -




tl;dr have 3PCs in use at home, unplugged cable from my PC put it into my ntb next morning internet wouldn't start, nothing helps, shows error that'S in a screenshot above, thanks for any help