Hello OliverWadowiec,
Good day! I'm John Dev a Windows user like you and I'll be happy to assist you today. I know this has been difficult for you, Rest assured, I'm going to do my best to help you.
What type of file are you downloading?
Please try this if it helps.
Press Start then search Default apps
Click Reset to "Reset to the Microsoft recommended defaults"
Restart your computer
if this does not work, please try performing a System Restore at an earlier date where everything still works.
Press Windows key+R to open Run then type: rstrui.exe
Press Enter. This will open System Restore
Click the Next button.
Choose the restore point at an earlier date where everything still works.
Click Next then Finish
Kindly let me know if this helps or if you have any further concerns.
Kind regards,
John DeV
Independent Advisor