Similarly, can you learn Sindarin?
Quenya and Sindarin are the most developed languages that Tolkien made, and the only ones someone can study, learn and use.
One may also ask, should I learn Sindarin or Quenya? In Sindarin, phonology and grammar are deeply intertwined in ways that are unfamiliar to most speakers of European languages (not the Welsh, though, since their language IS the prime inspiration for Sindarin!) Moreover, Quenya is by FAR the best-attested and most worked-out invented language in Tolkien's legendarium.
Beside above, can you learn Sindarin on duolingo?
Seeing that High Valyrian from Game of Thrones is being taught here in duolingo, it is only fitting enough to teach elvish as well (specifically sindarin). Elvish is not only a beautiful language, but a historical one as well. It has touched the minds and the hearts of people all over the world.
How long does it take to learn Elvish?
It's difficult. I started a course, but there is no way that you will start speaking the language. the only think you may succeed in 2-3 months of continuous study is to understand phrases and probably write down your own (but really slowly and always using the dictionary).