Lan cable on the PC slow?

I have connected a LAN cable to my PC. This is only recognized after 20 minutes and then very slowly at around 9 megabytes per second. I get 35 MB per second over Wi-Fi. On the other device, e.g. A laptop will display the LAN cable perfectly and also transmits 35 MB per second.

Now I ask myself whether the interface on the mainboard is broken or is it a matter of setting on the computer?

If so, do I have to order a new mainboard?

Or is it a matter of setting on the computer?

It will be exactly that.

If your LAN interface is defective, you can also buy a USB - LAN adapter or a PCIe LAN card.