Hi,
you can only work in Australia as a Physiotherapist if you are registered with the according Physiotherapy Board. No way around that.
A cheaper way for registration would be to get registered in New Zealand and then apply for the Australian/ NSW APC via the Trans Tasman Mutal Recognition. Only downfall in your case: the German physio qualification is not recognised in NZ.
Otherwise, you could work as a Health Care or Physiotherapy Assistant.
Regards,
Fyzzio