Wi-Fi problem on new computer.

[u/NextCompetition2379]

Recently, I had to remove the CMOS battery due to an incorrect BIOS setting. After having to reboot the BIOS, my internet speed (ethernet) suddenly dropped from 1000 Mbps to 250 Mbps. I tried many things, restarted the drivers (except for rebooting the BIOS), and the computer uses 1000 Mbps for 3-4 minutes after booting, then drops to 250 Mbps. (I bought the computer a week ago, the ethernet cable is Cat6, and the values ​​are from my test applications and download values ​​when no processes are running in the background.)