Try in Windows 10 in Settings, Notifications and Actions and turn Notifications off - this should hopefully stop notifications from apps and other senders (that's what it says next to the on/off switch anyway).
Unfortunately, this popup ad from Magix is not related to the Notifications of Windows 10. I have those all turned off anyway (and Magix is not listed as a Sender, either).
From memory, a while back there was a "Magix Connect" app that annoyed users. Check your apps to see if it's there in the Windows list of Settings/Apps.