Hi,
like in any other country with a Physio degree/ diploma, this information is part of your curriculum.

Here is a link to the German Ministry of Health page. Heaps of info there:
Bundesministerium für Gesundheit - Ministry

This is a link to a German Physio Forum, the category of billing:
Abrechnung und Heilmittelrichtlinien

Here is the link to THEORG, a software programme, which most of the German Physios appear to use for their billing:
THEORG

Hope this helps,
regards,
Fyzzio