so... repetition I find is very important for speaking and writing. Duolingo nails that. In the same way German class in high school did, hours of practice really helped my speaking. Now I can't really put together sentences - but I have a decent shot at deciphering my mom while she speaks to my grandomther in german, or reading an article. So I think duolingo attacks that nicely. If you want a lot of vocab and reading comprehension I think books are good for that.