Duolingo is awful. Sure, it helps you with memorization of phrases, but that's about it. With the heart system, it's absolutely abominable. The app doesn't explain grammer to you at all. Doesn't have any sort of dictionary. And the developers are just simply lazy, they don't add courses at all. I know lots and lots of people who have tried to volunteer to make courses(like for Farsi or Tatar), but Duolingo just never responds back. It's simply a lazy app that wants your money. Don't bother.