"Si parla" (si + the third person singular conjugation of a verb) is used to speak in generalities without there actually being a subject of the verb. It's usually more literally translated as "one speaks/talks", with "one" as the impersonal pronoun.
In English, though, we often use "we" or "you" as a pronoun to speak in generalities. "We don't speak" / "You don't speak" / "One doesn't speak" should all be correct translations.
Have you checked the previous comments?: https://forum.duolingo.com/comment/139617?comment_id=23564302