@Marvin_S I waited out a day just to be sure but I think the problem is solved. You might ask how, I have no idea. Thursday night I stayed up and tried everything all over again; switched between...

@Marvin_S They fixed the signal issue but the problem persists. As nothing changed for about 4 hours, I went back to Static IP with my set of DNS. I'm using PiHole on Pi as primary DNS and Google's...

@Marvin_S The modem is Netmaster Infinity 401. https://www.turksatkablo.com.tr/userUpload/sayfa/internet/kk/kk_infinity401.pdf It's in Turkish but as it's PDF I think It can be auto translated. The...

I tried to set Internet to Dynamic IP aswell. Did not solve it.

@Marvin_S Yes, I tried to change the cable. I changed both the cable between my pc and ax-53 and the cable between ax-53 and modem. nothing has changed Yes, modem is a router modem Yes, I tried to...

@Marvin_S I made a drawing about the situation. I cannot remove modem as I have a fiber cable coming to the modem. The ISP is mumbling something about signal levels but It was working fine.