"Are you drinking my coffee out of my cup?"
Translation:Trinken Sie meinen Kaffee aus meiner Tasse?
I'm Mr. Walkway. Mr. Walk down me, I'm the walkway. Lead me to the building...
I am becoming increasingly confused between Dative, Nominative, Genitive, etc. I don't think I'll ever understand it.
Are the using of Meinen and Meiner referring to the masculine and feminine of the coffee and cup?
Yes, they are. But they're also indicating the grammatical case. Nominatives would be: Mein Kaffee, meine Tasse.
Why is it meinen Kaffee and not meinem Kaffee? Do you just always use the plural declension for things like Kaffee?
I believe that that's because the coffee is the direct object, so that should be in the accusative case. The cup is the indirect object, so that should be in the dative case. Mein becomes meinen in the accusative case if the noun is masculine (der Kaffee), and meiner in the dative case if the noun is feminine (die Tasse). Hopefully somebody can correct me if I'm wrong!