@videomagic Open the Windows Taskmanager, go to the Autostart-Tab, check for a Magix software in this list, for example 'Update Notifier', disable it.

You can also uninstall it from Windows Apps and Features.

Magix asks during installation if you want to install this tool. You probably just clicked 'Yes' without checking what you installed. Be aware that this tool can be reinstalled if you run an installer again and just click 'Yes' to every option.