"People can pick up new languages over a period of a few years, but if you study it immersively, you can do so in a few weeks."

Can you elaborate on this statement? I think a few weeks is a bit of an exaggeration. However, I have known people who have gone from knowing nothing in a language to being able to have normal, everyday conversations in 6 months by being immersed and not being able to talk to anyone in their native language.