Questions & Answers about Dlaczego się ze mną kłócisz?
Why does the sentence use ze instead of the usual z for "with"?
The word z (with) changes to ze before certain words to make pronunciation easier. Because mną starts with two consonants right next to each other, we say ze mną instead of trying to pronounce a difficult cluster like z mną.
Where does the word mną come from?
mną is the Instrumental case form of ja (I). The preposition z (with) always requires the following word to be in the Instrumental case. So, to say "with me", we combine ze and mną.
Why is się separated from the verb kłócisz?
The dictionary form of the verb is kłócić się (to argue). However, the word się usually avoids sitting at the very end of a sentence. It prefers to jump earlier into the sentence, often landing right after the first word, which is Dlaczego here.
How do we know it means "Why are YOU arguing" if the Polish word for "you" isn't there?
In Polish, the ending of the verb tells you exactly who is doing the action. The -isz ending on kłócisz specifically means "you" (singular, informal) are doing it. Because the verb makes the subject so obvious, the pronoun ty (you) is usually dropped.