Problems with block multiple filter

Hello,

I have following problem with the block multiple filter displaying the correct posts by category – here an example:
1. I have the category 1 “Brussel” and the category 10 “Monument” and other categories 2, 3, 4 for the cities “Antwerpen, Gent, Knokke”.
2. I want to display on the page “Brussel” the “Monuments of Brussel” (that means category 1 and category 10)
3. But by selecting these two categories in the block multiple filter all (!) posts with category 1 “Brussel” and all “Monuments” with tagged with category 10 are displayed – so also the monuments of Antwerpen, Gent, Knokke too.
4. Do I have to exclude all other cities with “-category ID” – but this would be laborious or long-winded!
5. Or do I have to build up categories like “Brussel-Monuments”, “Gent-Monuments”, “Knokke-Monuments” and select this in the block setting filter by category like a single filter – but then the “multi categories filter” would be superfluous!
6. The right way from my point of logic has to be: By selecting in the multiple category filter “category 1, category 10” only (!) monuments of Brussel will be displayed and not all (!) monuments (of other cities) and Brussel will be shown.

Do I’m understanding something wrong in building categories or using the multiple categories filter?

Thanks from Germany
Michael