This site has specific information on Australian soils for you Angelika.
Au soil types
When we are starting out with already degraded soils, we do need to make some amendments, this allows us to get at least some crop for our efforts (and it can keep your desire up too so you don't get discouraged).
This set of amendments along with the roots those plants provide are the start of the building process, there is now material for the microorganisms that we want to begin adding to make that soil better and better.
The better the soil becomes, the less amendments we should need to add, because we are building soil that will take all those minerals and other nutrients and recycle them in a continuing circle of life.
This is where the soil test is a big help, at the beginning of our soil building adventure, once we have the soil built up with microorganisms, a soil test will show just how well we are doing (most of the minerals and other nutrients should be available).
That is our goal, to not have to make continuous additions to our soil so things will grow.
In true deserts it takes a little longer but it is happening even in the Sahara.
In these sorts of places first we have to get water to hang around and from there it becomes easier every year.
For most of us this whole process is just that, a process, so we plug along as fast as we can afford to.
Redhawk