I grew up in a multi-lingual family and took Spanish in High School. I do recommend Duolingo. I am improving, and I hope the company continues to improve the app. I am using it for my own practice and for my students. Their confidence is growing.
I do like the different ways questions are formatted: translate a phrase, choose one, match word to picture, listen and translate, speak the words, choose words and place in order. The varied methods do work similarly to how children learn a language, but their understanding will only be basic.
This app does help me practice, but I need instruction regarding conjugating before I am thrown in to answering questions and making translations. Without instruction, learners like me never make the correct uses permanent because we do not understand what we are to do and only retain what we did wrong. The wrong choice becomes the only thing we remember clearly, and we havent the tools to make the correction.
SKirtonBear2 about Duolingo Learn Many Languages for Free, v5.0.14