Steps
- Open Calendar and select “Import calendar” under linked calendars.
- Copy the Check24 export link.
- Create a Check24 source and paste that link as its import URL.
- Copy the kalenderabgleich.de export URL and import it into Check24.
- Remove every other connection.
Final step: Remove all old direct calendar connections to other portals from the provider. Only the kalenderabgleich.de calendar should remain connected.