There is no configuration option for caldav online calenders on the phone. But on the desktop version there is such a option. Therefore I configured the calenders on the laptop and copied the configuration files, like this:
florenz:~/.config/evolution/sources :) $ scp 61a78e92b354d1a429fc89f8bf339cc32c3f298a.source mobian@mobian:.config/evolution/sources
If one shutsdown the phone with the charger plugged in the phone starts again after shuttding down, because external power is a signal to boot.
The solution is to disconnect power before shutdown