Duolingo is currently having more than 72 languages of the globe. I am using it since 6 months and I am 51% fluent in Spanish.
It is a playful way of learning. Best of part of this app is that you keep learning with the help of games. Duolingo team has designed it in such a way that your language will keep getting better and fluent. It even has a feature that calculates the fluency.
But if you want to be a pro speaker in any language, I don’t think this is an ideal app for you. For beginners and basic learners, kudos to the app