Learn Polish: Czy mówisz po polsku?

Czy is a question word used to start yes/no questions. It doesn't have a direct English translation, but it acts like the "Do" in "Do you...". You don't strictly have to use it—you can just say Mówisz po polsku? with a questioning tone of voice—but starting with czy is the standard way to make it clear you are asking a question.

Where is the word for "you" in this sentence?

The word for "you" is built right into the verb. Mówisz specifically means "you speak". Because the ending of a Polish verb changes depending on who is doing the action, pronouns like ja (I) or ty (you) are usually dropped unless you want to add special emphasis.

Why do we say po polsku instead of just the standard word for "Polish"?

When talking about speaking, reading, or writing a language, Polish uses the word po followed by a special form ending in -u. So po polsku translates roughly to "in the Polish way" or "in Polish". You will use this exact same pattern for other languages, such as po angielsku (in English) or po niemiecku (in German).

Why does the word mówisz have a line over the letter "o"?