Syncronization QNAP or Win10 with Nextcloud

Hello all,
I have a question about a decent app or other application that allows me to sync with Nextcloud either directly from a QNAP NAS or via the Win10 interface. On the PC I already have the Nextcloud desktop client running, which synchronizes individual directories in real time - everything works fine. Now I have directories, which are much more extensive (so 500GB and more ) these would also NOT have to be synchronized in real time, but it would be enough to expire in the evening or at night. I have already tried to realize this with a WebDAV link via HBS3 with QNAP, but that does not work, that breaks with the amount of data again and again. And via the desktop client it does not work either, that blocks the real-time synchronization. So I would be really happy if someone had a suggestion or even a solution how to implement this.

Thanks a lot, Dietmar