Oh Robin, this is TRULY insane.
I have read your post five times and I still don't understand it.
Advanced mathematics is simpler for goodness sake.
I honestly don't think I can ever learn this.

It seems like it was complete chance that I got the дом right in my example. It was not because I had understood it right anyway. And someone was mentioning other language skills, well the truth is, my Spanish and French are really bad - and the grammar is a lot simpler for these languages. I can not have serious conversations. I don't count that as languages I really speak. And German, I won't even mention that, it's strictly pidgin style. Basically I am not very good at languages.

I managed to learn English without knowing any grammatical terms and I have reluctantly learnt the basics of grammatical terms, just to study Russian. But this is just too hard.

Virtually any programming language for example, is a breeze compared with Russian.

I used Дома because I thought it was nominative plural!!!
apparently by complete chance, it is the same word in genitive singular (que???)