Elaine wrote:I have got a question:
Does the accusative object become a genitive object when the sentence is negative, like Polish and Russian does?
Nepiji čaj - Nepiji čaje
Čaj is a bad example, because it doesn't have a plural (I mean it does when you're talking about types of tea, but just like milk or beer you have to quantify the mugs, cups, bottles and whatnot)
Jím jablko. Nejím jablko. ( no change in cases)
When you see Nejím jablka. It's plural, not genitive.
Bez jablka. (Gen. Without an apple)
P.s. Piji is too formal. Even though it's correct, piju is what you'll hear 99% of the time.