I occasionally play tennis with a professor of linguistics, and he told me that Arrival (mostly) did a great job of portraying how one might theoretically go about deciphering an alien language. When’s the last time you saw a movie about your profession that wasn’t rife with errors?
Accuracy aside though, it’s just a really good movie (and critically, one that rewards rewatching), so you can rent it from Amazon for just $1 right now.