apt install php-bz2 php-curl php-gd php-imagick php-intl php-mbstring php-xml php-zip owncloud-files
I don't know... I think I reconfigured so much it got confused. I had to create a new entry and then it worked.
Leave Remote Subfolder empty
Check Secure https://
Use Username and Password as Authentication and put nas' WEbdav credentials, also in cloud entry notes in KeePass