I recently tried duo lingo. I have a pretty strong background in Spanish, but want to brush up. It became apparent very quickly that the app is not about learning so much as keeping you in it. The lessons don’t make a ton of sense, and after not using app for a week, it demoted me to just 8 words that you would learn in your first class (hombre, el, agua, tu, etc.). There is no way to skip ahead.