Learn Polish: Ilu prawników nie pije kawy? - How many lawyers do not drink coffee?

Ilu is the special form used for groups that include at least one man (masculine personal nouns). Since prawnik (lawyer) is a masculine person, we must use ilu. For objects, animals, or groups of only women, you would use ile.

Why is the noun prawników in the Genitive case here?

Quantity words like ilu (how many) or wielu (many) always force the noun into the Genitive plural case. The same thing happens with numbers 5 and up.

If we are talking about multiple lawyers, why is the verb pije in the singular "he/she/it" form instead of the plural piją?

This is a surprising but very important rule! When the subject is a quantity word like ilu or a number taking the Genitive case, the verb must be in the 3rd person singular form. So grammatically, it acts like "how much of lawyers drinks".

Why does coffee change to kawy instead of using the direct object form kawę?

Normally, drinking coffee uses the Accusative case (pije kawę). However, the word nie flips the direct object into the Genitive case. This is called the Genitive of negation, which turns kawa into kawy.