Usecase and translation

First of all you need to reset your permissions to get back in! Click on Church Admin, then Settings then Permissions – if you are an administrator that will work. Check the checkbox for Delete all user permissions and then Save

Permissions issues are usually because directory entries have not been connected to wesbite user accounts – edit the people who will need access and use the dropdown to select the account.

* Can I give several team members the exclusive right to create new calendar entries?
Yes – The permissions setting allows you to do that as long as tehdirectory entries are connect to user accounts

* Is it possible to create parallel appointments in different resources (rooms)?
Yes but individually for each room/facility or category

* Is there any collision detection for events (same time period with same resource)?
No

* (How) Can I change / edit the Plugin text constants (plugin translation)?
Go to and register or login top left.
https://translate.wordpress.org/locale/de/default/wp-plugins/church-admin/

As you can see someone has done it (possibly badly) as no editor has approved the translations. If you can apply to be an editor for Church Admin you can bulk approve the translations.