Syncronyze contacts with empty Nextcloud. Who is main, server or client?

Nextcloud 17.0.1
Arch Linux
Gnome 3.34.2
Contacts 3.34

I used Nextcloud to synchronize contacts.
In my Gnome I have configure Nextcloud account.

This means that contacts and calendar are integrated with the system.

I reinstalled Nextcloud server and now it is empty.
But I have contacts in my Gnome app Contacts.

What will happen if I turn on synchronization with Nextcloud:

  1. Contacts from my desktop app will be downloaded to Nextcloud server?
  2. My contacts app will be empty, because Nextcloud contacts are empty?

It’s probably best, if you go ahead and export/save all your contacts and appointments before connecting to the new NC instance. That way you can be sure to keep all your data. It might be the case that your current contacts and appointments are cached in your contacts app on your desktop, but they have to be tied to your old NC account.

If you setupo a new NC instance, then there will be a new account ID, so I could only speculate, what the inital CardDAV/CalDAV sync will do…