Hi @Martin2607; thanks for joining the Community!
It's true that sometimes when you delete files or folders, they don’t immediately disappear from every synced computer.
If you happen to have a synced computer running an application that is using the file, it will cause the file to reappear in your Dropbox account. Or, if you’re seeing a shared file or folder reappear after deletion, it may be that a person you shared it with is accessing or restoring it.
To see if that's the case, can you check a sample file from inside of the folders that are returning to see its version history on our website?
If you check the previous versions of the file and see that it was accessed from an application on another computer, you can delete it off of that computer to stop it from reappearing in your Dropbox.
Keep me posted, Martin.