Is it possible for an Australian citizen to acquire German citizenship and keep their Australian citizenship?
(All the links I've been able to find are going the other way—about Germans retaining their German citizenship upon taking up Australian.)
Germany does generally not allow dual Citizenship, so they will ask you to resign the Australian citizenship first.
There are exceptions, of course:
For an exception, typically you need to prove strong personal bindings to both countries, significant employment consequences (limitations), or specific financial hardships that would come from not having either citizenship.
Personal bindings could be ongoing longterm relationships, family, etc.; be ready to prove it - 'we are phoning all the time' is not enough.
Employment consequences could be you cannot apply for a significant part of your qualified jobmarket without the citizenship, like missing security clearances that only citizens can get.
Financial Hardship could be you have a mortgage in the country and you would not be able to refinance without being a citizen, etc.
The list is not exclusive, but should give an idea of the level of convincing arguments needed.