Thanks for your quick response. 
Actually I’ve seen that if you give administrator privileges, instead of content manager.It seem that Duplicati can delete only the file that he is the author, but when the account on the shared drive as a content manager privileges, Duplicati can’t delete it’s own file. It seem that in content manager Duplicati’s files are granted to another person. So he can upload and modify but when it’s about to delete, he cant do anything.
I think the solution is to give Duplicati Administrator right on your shared drive.
Also I’ve seen that the default password to open the database is
Duplicati_Key_42
[source :] (Clear text password stored in Duplicati-server.sqlite - #17 by kenkendk)
Because I want to make sure that if for example someone want to mess up everything, he could get the password, unecrypt the database, get the credentials for any repo and then do everything.
If it’s the case, I have a feature request I think x)
I’ve read that Fix not revealing stored passwords from the UI [$100] · Issue #2024 · duplicati/duplicati · GitHub and Are backup encryption passphrases always stored in plain text? - #3 by ts678
But when I want to open Duplicati-server.sqlite I can’t read it with DB Browser for sqlite. I am doing the wrong method?