Nextcloud not syncing local folder to web interface

Hello everyone,
i’m kinda new of nextcloud and i’m facing a little problem…
i have set up a working nextcloud docker, created a folder on the web interface, and it appeared on the local server. That’s perfect.
the problem start when i put some file in the local folder, it gets written, but when i go to the web interface i cant see the file…
test
as shown in the picture, left is my FTP program that shows the right path to nextcloud folder, right it’s the web interfaces that shows No File…

In the future i will have a third party program write stuff in that folder, and i would like to get it working so i can share that folder… am i missing something? is there a way to make it working reliably?
Thanks in advance for your help

I think you do not understand sync with nextcloud. Sync only works with the nextcloud clients for Windows, MacOS, Linux, Android and iOS.

If you upload files with e.g. FTP Nextcloud can not see it. But you can make an re-scan of the user or all with:

sudo -u www-data php occ files:scan --all

https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/occ_command.html

Then Nextcloud includes the new files in the database. But please test the nextcloud client apps. You do not need FTP for upload files.

The problem is that i cant use a client, file are generated in 1 folder of the server, and moved in that one… so there is no way to use a client, and the solution then is to add a cronjob to scan the folder every 15 min, or i need to find another program that allows me to do that…

Yes and No.
If you use WebDAV your problem is solved.
With WebDAV your Nextcloud includes uploaded files.
Read Access WebDAV.

Windows:

net use Z: https://example.com/nextcloud/remote.php/dav/files/USERNAME/ /user:youruser yourpassword

my nextcloud installation is in docker, and my third party program that is gonna save file in that folder is another docker, is there a way to do it? i’ve read that article but it’s not talking about servers, only windows linux and mac client