Not to be all Debbie Downer, but as a language teacher I really, really don't recommend Duolingo, or really any similar app (Babbel, etc). All they can do is help you memorise certain pat phrases, but they can't teach you to speak or understand the language in any meaningful way. I'm fluent in French, and tried the French lessons on both Duolingo and Babbel, and had the same issue with both--many of the phrases they teach simply aren't used or aren't the best way to express the idea that they say they want you to express. The interactions are stilted and don't mirror natural language or natural conversations with native speakers. To an extent, this is always true with beginner language lessons; much of it is memorisation because it has to be, but I was working on the Intermediate--Advanced lessons and it didn't get any better.
If you want to learn French, I'm a qualified teacher and I can do lessons on Skype. Discounts for UKY members!