Nobody will dispute the fact that the best way to learn a second language is to live and work with native speakers. This is most effective when you are a beginner. But if your goal is to reach an advanced level or, better yet, become fluent and your time is limited then you will have to study. It doesn’t take a genius to realize that the most common words, phrases, verb tenses and structures that you will come across in your daily encounters with native speakers represent only a small part of the language. This means that you will have very few chances to hear and practice such things as indirect questions and mixed conditionals. Only with a teacher or in a class, where you can drill these structures, will you have the opportunity to master them. As in sport, it’s the coach that elevates the mediocre athlete to greatness.