Computer NAS infrastructure for 7 computers

I bought a Synology NAS device and need assistance setting it up in the company. We have 5 computers being used. I would like to have a system of shared files. (similar to OneDrive)
Forexample:
One computer is for sales
one computer is for accounting
one computer is for PRO
one computer is manager

I want to be able to see everyones files
i want no one to see certain accounting files
i want no one to be able to delete certain file from certain folders.....etc

I need a full system up and running. Given the size of computers in our company.
Please quote your price