Some questions on languages.

Hello everybody,
I am a spanish young woman interested in early education, I browse this forum and I thought it was very interesting so I decided to subscribe. First I must say that I have no children, so sorry if I look ignorant. I am especially interested in languages, and I would like to ask a few questions on that subject.

  1. As far as I have read many of you are teaching languages that you don´t know very much about, and you use products like DVD, audiobooks and flashcards. Is this enough to learn a language? When did the results show up?.
  2. Many of you are teaching more than one languages, I would like to know how many of them can children learn. I mean, is there any limit as to how many languages kids can learn? (When it comes to your experience or reasearch done on the matter).
  3. As the kids get older, is it difficult to maintain the/those language(s)?.

That´s about it. I would like to thank you in advanced.