Here’s my background in languages – my mother tongue is Filipino, I have learned English since pre-school and I took Dutch classes for 15 months. I speak these languages everyday but none of them really ever bothered me so much with grammatical cases.
So what are grammatical cases? I leave you to Mr. Wikepedia to answer that. This much I know, Spanish language uses genders (like the Dutch het/de), German uses gender and four cases. The Russian language uses Cyrillic, has gender and uses six cases!!! And I have only learned (barely) three cases – the easiest is nominative and the two other, which have almost sent me to a nut house, are prepositional and accusative.