Originally, there was the problem that booking a service also marked all other services as occupied.
This was treated in thread "BOOKING A SERVICE ALSO OCCUPIES ALL THE OTHER SERVICES" https://premium.wpmudev.org/forums/topic/booking-a-service-also-occupies-all-the-other-services#post-1202675.
The proposed solution was taken over by the customer.
Now, the problem is that a booked service is no longer displayed as occupied. See the screenshot.
You have support access and can see it live http://www.ks-wn.de/?page_id=3863&app_service_id=2#app_services_dropdown_title , when you are logged in.
Your help is very welcome.