OK. I see what you're trying to do.
At the moment, I don't think CR is doing anything wrong as far as the Sorting goes - it sorts both the positives and the negatives for each group correctly.
Having said that, you cannot sort a crosstab on the same summary field in two directions. What you can however do, in this situation, is that convert the negative values to positive using the abs function and then do a lot of formatting using the 'Display' string function to make them look like negatives again.
Have a look at the updated report I've attached. Things that have been done:
1) The Summary field of the Crosstab is now based on a formula (called Summary). The Summary dynamically converts values in the Koszty group to positive values.
2) A Display string formula then takes care of the signs. It prefixes all the values in the group 'Koszty' with a negative sign
3) The same formula also takes care of the zeroes from being shown up
4) The Display string is applied through the crosstab - in the Symmary fields, in the Subtotals and Grand Totals as well.
I hope this is what you were looking for.
-Abhilash