A couple of things I've always wondered about

[Reiey fpi Sìtaron]

Couple of things that I've been thinking about recently, and I want to hear other people's opinions on them :

1) Has a Na'vi ever been taken (voluntarily or otherwise) back to Earth? If so what would have happened to him/her?
2) Who learnt the others language first? Did the humans learn Na'vi first? or vice versa. How was Na'vi "deciphered" to begin with?
3) What was the first human-Na'vi encounter like? violent? peaceful?

I'm interested to hear what you guys think about this, maybe there's something I haven't read yet that you have on these?

[Seze Mune]

Good questions, but I don't think much of the backstory has been engineered on this yet.  Future movies might deal with it?

[P.A.'li makto]

Who learnt the others language first? Did the humans learn Na'vi first?

I suppose they learnt each other's language simultaneously. It's the only way I can imagine the process.