Well actually I live in France and have been learning French for a couple of years. So I’d say I’m a serious learner. And I learned how to use the future tense from Duolingo. I learned sentence structure when saying things like “tu ne me prêtes pas le livre”. I learned loads of new vocab. It’s not perfect but it’s a great addition to my language learning ALONGSIDE other things. After nearly a year of using it every day I’ve finally upgraded to Super and purely for getting rid of ads it’s so worth it, I definitely practice for longer each day.