Lol that friend must have been really interested in those english books :D. I wish I could’ve saved you from spending so much money on rosetta stone because it’s really expensive and language is a free thing plus there are much cheaper resources like germanpod101 which has every tool you can think of (check it out) , the live classes is a waste of money, there is a site that I use when I want to find friends it’s called mixxer and all you do is go there, choose the language that you’re learning and you’ll see a bunch of people who speak the target language and want to learn your language, you can just send them a message meet on skype and you’re all set, you teach each other, I met a few french friends on that site in 2014 and we’re still friends.
next your right about languages having variations like spanish, they speak slang which is considered colloquial speech which exists in every language and there is both south american spanish and european spanish which has slight differences.
and finally you’re right about being engaged in the language and making it a part of your everyday life, now i’m studying japanese so after gathering all that information back when I studied french, I now apply them to my japanese studies, I focus more on listening now, vocabulary flashcards which works, I watch a lot of anime because I love it which helps with listening and i listen japanese music and so on.
(I’m sorry, i mixed free resources with paid resources, I don’t really have any money so I get anything and everything free online. this is why I started this conversation about rosetta stone but I mean no harm)