Hello @Johannes ,
Community Document Server is not our application, for more information please check out this topic: Community Document Server app in Nextcloud 18
We do not provide support for this app as it was developed by Nextcloud team, but you can contact Nextcloud team instead.
Here are our official guides of Onlyoffice Docs installation: Installation Guides - Docs - ONLYOFFICE
We recommend that you install this version and connect it with Nextcloud following our official guide: Integration. Getting Started. Nextcloud - ONLYOFFICE