I work on a database with a friend and we sync it by Dropbox.
Our goal would be to have it on a server (not just on our Macs) so to be able to give access to docs to all our coworkers.
Is it possible in some way?
Tks! 
No, this is not possible. DEVONthink databases are not made for simultaneous User access. We advocate a decentralized data model where each machine has a local copy of the data but Syncs to a commonly-accessible location.
If you are using DEVONthink Pro Office, there is a Web Sharing interface that allows Users to access a broadcasted database in a web browser.
Note: Web Sharing is ideal on a LAN. If access via the Internet is needed, proper port forwarding needs to be set up. Port-forwarding is equipment and environment specific. Check out DEVONthink’s Help > Sharing your data for some hints on this, but you may need to consult with your IT department or router manufacturer for specifics.
Alternatively, you could be indexing data in a commonly-accessible Dropbox location, but you should search these forums about indexing (paying extra attention to posts by Greg Jones, as he uses indexing almost exclusively). Indexing should be carefully considered before jumping into it.
Wouldn’t it be a nice idea to put at least little security by means of a padlock and https:// in there?
Excerpt from hell (DTPO help) to get data even thru the internet (OMG!):
…
If everything goes well, you will be able to access your database using an address like: http://xxx.xxx.xxx.xxx:port, where xxx.xxx.xxx.xxx is your current IP address. (Note: This is your router’s address, not your Mac’s.) Next, port the outside port number leading to your published database.
…
Even on an intranet transfering unencrypted credentials and content is ugly and 90’s… 
And over the internet?
Well, to speak in terms of security (GDPR?): it’s 
and hardly sanctioned in businesses (at least in the EU).
BTW: I love DTPO and DTTG - thus I encourage you to get rid of offering unencrypted service http:// in your app even on local net - even more in written (help-) suggestions for crossing internet with valuable credentials and/or data unencrypted.
20 million (€) good reasons to avoid. 
Set up a reverse proxy with Nginx or Traefik and do ssl support from there. I personally run a setup where I use Traefik on a VPS with ssl from lets encrypt and I use a Zero Tier One VPN for secure access between the server and my Mac. Traefik will auto renew my certificates which makes it a nice hands off experience. I give all of my web apps SSL support via reverse proxy.
Now if you want to be fancy, you could set up login auth on the proxy side that connects to Active directory and only allow your IT department access their powerful wiki 
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