I spent a week troubleshooting this issue with slow internet speed. I tried everything I could find and found the fix. I know I had 750 plus MBPS at the computer but my computer kept downloads at 330 MBPS. After all kinds of settings that I tried it came down to the command below, try it yourself and see if that fixes the problem you may be experiencing. I had mine originally set to disabled.
Netsh int tcp set global autotuninglevel=normal and press Enter.
FWIW, that is the default value for any "auto-tuning" Windows operating systems..