Hello Lenny, welcome to the Microsoft community, I'll be happy to help you today;
I understand that you are having slow internet issues.
Initially I recommend that you check if you are updated with the latest version of Windows 11;
Press Windows key + i and go to Windows Update;
Click Check for updates and do ALL pending updates;
Run the troubleshooter;
Press Windows key + i and go to System;
Click on Troubleshooting and then on Other Troubleshooters;
Locate Internet Connections and click Run on the right;
run a disk cleanup;
Press Windows key + R and type: cleanmgr press Enter;
Click on clean system files and wait for the files to load;
Select all files and click ok to delete them;
Perform a clean boot;
Press together the keys: Ctrl + Shift + Esc to access the task manager;
Click on start and disable all programs that start with Windows;
Before restarting the PC do a network reset;
Press the Windows key and access Network and Internet;
Click Advanced Network Settings;
Click on Network reset;
Click Reset now;
Confirm the operation and restart the PC;
Check if the problem still persists;
See you soon!