I read Steve Sololon and worked out the sheets. But if I look in google there is a lot written that there is no scientific evidence that minerals have to be in a certain balance. I don't need scientific proof to believe something but is there enough evidence to support that? My gut feeling says yes because there is something similar happening in the human body.
I read somewhere that I can "flush out" too much potassium with calcium? True? Should I then go over the target levels with the calcium? I didn't do that for most of my autumn planting but could do it in spring.

The thing about minerals is that almost all soils have most all the minerals needed already there, they might not be in water soluble forms (which is what just about every one talks about) but they are there.
It is the microorganisms of the soil that are capable of bringing these present but unavailable minerals into a state that the plants can use them.
What you have to keep in mind is that in order for anyone to talk about minerals, they have to be dependent upon soil testing to be able to know what water soluble minerals are present.
This means they are resorting on the same data and test technology as the commercial farmer and thus are looking at artificially providing what the soil tests say isn't there in enough quantity or too much quantity.
When you start down that road, you might as well jump into the till the soil to dirt and add all the "nutrients" to grow a plant to minimum nutrient viability, just like the commercial farmers have been doing for the last century.

Far too often people want to become permaculture method users but then they get into relying on the incomplete data that has had a choke hold on commercial farming since the development of soil testing.
That means you are looking to part of the unsustainable technology as the answer to sustainable agriculture practices.
That just doesn't make good sense, the soil tests are good up to a point, but after that, they are giving false data to the sustainable farmer or gardener.

Bacteria and fungi use enzymes to break down rocks (rocks are minerals held together), once the rock is broken down, every item that made up that rock can be further broken down and will end up usable by the plants that told the microorganisms to break down the rocks.
That means the minerals that could not be detected by soil science laboratory techniques, since the minerals were not in water soluble form, become available. This can cause an overload situation if you took the test results and added all the "missing" items from the test.
Now you have all those minerals you added and the microorganisms are providing more of those minerals through enzyme production and action, which causes there to be an overabundance situation.
This can create leaching problems from a glut or it can take out some of the needed minerals by chemical bonding with some of the glut.

Soil tests are good, they give us an idea of what we have already available to our plants.
They do not tell us what minerals there are in our rocks nor how much of those minerals are in our rocks.
Any time you start making additions, you are going in the non sustainable direction.
It would be better to build your soil microorganisms than to start adding minerals straight away, you might find that after your soil is built well that you find that your first soil test was way out of whack with the results of the post soil improvement test.

Redhawk

In short words you think that it is not that important. Our soils according to the map are: Kurosols, Rudosols and Tenosols whatever that means but they are all classified as unsuitable for agriculture which I found in a poster here: Australian soil club. That means do they still classify as having enough nutrients to get things going (hmm for the type of soil my garden is doing very well apart from the brassicas and beetroot).
Is there any credit for the balance of nutrients like calcium/ magnesium or so?

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

Is there any credit for the balance of nutrients like calcium/ magnesium or so?

Oops, I didn't address this question in my first answer, my apologies.

Yes there is a need for balancing nutrients, excess of one may hinder the ability of uptake of the other, such as the calcium magnesium pairing. which would turn into magnesium calcite crystals and that wouldn't be usable by your plants until the right bacteria (that make the enzyme that breaks this compound down) were present in large enough numbers. pH also needs to be considered since too acidic will bind one set of minerals and too basic will bind another set of minerals.
The reason we try for a pH of 6.8 -6.5 is that this range of very slight acidity allows for the most minerals to be available to the plants overall.