[tmd]

After having lived 4+ years in Germany and struggling to learn German, I would say that the only way you can learn truly by pure immersion is from your parents. In any other case you need at least some theoretical basis because no one else is willing to spend hours trying to communicate with someone who's basically babbling.

I'm using Duolingo now and after I'm finished with it I want to get some formal classes to (hopefully) get to a B1 level. I wouldn't call Duolingo immersion learning though -- they explicitly provide grammatical rules (unless you're using the mobile app which lacks some features) and it's very difficult and frustrating to try to do it with your intuition alone.

I also liked the explanation of cases and adjective endings from this site: http://yourdailygerman.com/learn-german-online-course/