How did you learn languages to navigate this world, pirates ?

My friend is looking for a resource to become fluent in French, he is forced to work with it. Asked to find a certain book, but it is not yet pirated on the resources of the wiki. My guess is that pirates have better alternatives for such a thing, so I'm launching a discussion.

I only ever heard about the book "Minna no Nihongo" in the context of learning Japanese.