This article got me to looking around in Windows 10's notification settings.
When you've got time on your hands go to these pages in Windows 10 settings and judiciously turn things off.
Windows key + Notifications & Actions
You can also click on the icons in the list "Get notifications from these senders" and fine tune each app's notifications.
Here's what Dropbox's looks like.
Windows key + suggestions
Look around. You'll find lots to tweak.