Yikes! - This may be a stupid question - but what were you testing: Tap Water or Tank Water.
In addition to the suggestions above, here are some of my thoughts.
No on the Kalkwasser (BTW
the literal translation of this, from german to english, is "Chalk Water" - better known as Lime Water). I'm pretty sure this will most likely make matters worse at this point.
If it is your tank water that you posted the stats on - then test your Tap water and compare. If it too is very high then you have a supply problem (You do not mention if you are RO
'ing your water - this will take much calcium out as calcium molecules are to large to pass through the TFC). If you are RO
'ing your water it may be time to replace your TFC, sendiment cartridge and carbon element.
Also be aware of some hidden causes of high gKH and dKH
: Substrate (some are very high in calcium and carbonates), Decorative items (some rocks and stuff contain limestone, etc), chemical additives you might be using - i.e. buffers, etc.
One buffer product I know of instructs users to add x tablespoons every water change. This is pretty bad advice as it is intuitive that you should only do this if you need additional buffering. Wholesale addition of this kind of product can cause trouble.