Whole PC starts lagging and freezing when using high bandwith of Internet

[Henriklmao]

A couple of months ago I have upgraded from WIFI to Ethernet. Max speed beforehand was around 35-40mbps. Now with the lan cable, it is between 300 and 900. For some reason, my whole pc starts lagging and freezing when I download many things simultaniously, any Game Launcher is updating or when my Windows does an update. Also this happens when I'm playing Microsoft FlightSimulator because it is loading all the world data from the Internet. I also have bad performance in games when my AV is doing a scan.

May anybody have a solution for that problem? I have malwarebytes premium and I have done the antirootkit and some full scans, so it shouldn't be a virus right? Maybe it is some problem with my m.2 ssd but I've ran several different tests and there's no bad sector whatsoever.

I'm running the latest version of Windows 11 insider on a ryzen 7 2700x, 32gb ram and an RTX 2060s (latest driver) and a 970 evo plus nVme m.2 ssd.