For anyone who wants to learn a language, you have three options: the class, the app, or the stranger or friend. Say how are you in a number of languages and learn how to say sir and pal buddy or dude comrade ecetera in different languages. Once you know languages you can study demographics. A tutor may or may not be necessary. The more fluent the speaker you find the better.
Rosetta stone is a good program but absolutely impossible to train you for a real position whether that be something like a teach or possibly the government. Personally I beleive it doesn't matter how long it takes to learn new words, as long as the words are understood well.
To start avoid complex thinking. Its easy to get confused with a stranger.