Trying to sync Synology NAS via webdav with nextcloud


As topic is saying, I try to sync my Synology NAS via webdav with nextcloud on a dedicated server and I’m even not quite sure if it is a problem with nextcloud.
If I try to connect like this
I get an "Connection denied"
If I misspell the password intentionally I get an "authantication error"
and that’s also the only thing a can see in logging

Warning core Login failed: ‘user’ (Remote IP: ‘’) 2017-10-31T14:29:54+0100

Access via Firefox brings this message:

This is the WebDAV interface. It can only be accessed by WebDAV clients such as the Nextcloud desktop sync client.

Actually I have no idea what I’m doing wrong.

Best regards

Nextcloud version: 12.0.3
Operating system and version: Ubuntu 16.04
PHP version: 7.0.22

As almost always the guy in front of the monitor was the problem.
I was trying to establish a remote connection what seems to a total different story.
Now I’m really using cloud sync and everything works like expected.

I’m sorry for that!

Best regards