I fixed it! You wouldn't believe what it was, so here is the solution:

The tcp auto tuning level was off

so i opened up a powershell via Windowskey-x (admin rights) and applied the neccessary changes as you can see in the screenshot:

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I also disabled heuristics. Heuristics is a feature that can interfere with auto-tuning and disabling it can improve Internet speeds and in fact heuristics have already been disabled in Windows 8.1 and greater. Auto-Tuning on the other hand should NEVER be disabled.