How can I progress faster?
I've been learning Russian ( on Duolingo only ) for like a year or more, and I am not even 70% through the tree. I do not start a new skill unless the one preceding is gold, and the words in it are nearly unforgettable and practiced a LOT of times. The problem is that I "fear" finishing the skills fast because I think I will be forgetting the words in a couple of months or will not use them in their right places.
So, is that normal? And how can I get over it because it is slightly ashaming to be so long in a single course?
Note: I am speaking here about languages as a whole; it is not only Russian.
Forget about keeping your tree gold and start talking to native speakers. Using a language is both the best way to cement its structures in your brain and the best way to improve.
When it comes to keeping vocabulary in your head, use a flashcard program like Memrise. It's more efficient and more effective than repeating Duo's lessons over and over again. There is such a thing as too much revision, so get out there and start using what you've learned!
You can still keep practising after you've finished the tree. I'd only really properly learned about half of the lessons when I finished the Spanish tree after 6 months, but am getting close to knowing all of them now (after a few more months).
I actually wondered if your approach might be better, but on reflection I decided it probably doesn't make that much difference.
The aim is to learn the language, how you get there is less important.