I just finished the German skill tree!
I just finished the German skill tree. I feel great. This is not my first contact with the language. I have already gone through German texts for many years now. I am not studying German on a regular basis though. Neither I do study it intensively. I'll keep working on it . Since I learn it mainly for pleasure I find this rate is fine.
It took me about three months. Maybe a little less. I reached one crown on each skill because I wanted to complete the tree as soon as possible. I used Duolingo as a refresher. Earlier I learned quite a lot from courses by Deutche Welle and from books. There are some very good dual --German/English-- books (Penguin books, Dover, etc.) with stories by well known German authors. They help a lot in the quick acquisition of vocabulary.
Fluency, certainly not. It is a good introduction though. You can also go through courses on the page of Deutsche Welle for free. Language is an immense field. It's study never ends. When you reach an intermediate level you could try parallel texts (e.g. in Penguin books) Your vocabulary will augment quickly.