Hey @claaauu, thanks for reaching out to our Community and sorry to hear you're having trouble with this.
It sounds like you enabled the computer backup feature and your files were backed to Dropbox, when you deleted the Dropbox folder.
That would definitely cause them to get deleted. Have you checked the deleted files page in Dropbox?
How about your events page?
Make sure to also check in your computer's trash/recycle bin as well.
Let me know what you find.