I was never good at foreign languages in school. I failed my French classes each and every year and my English was as good as I could learn it through what I got from Hollywood. This means forget about s/z differences (pun intended) and please don't get me started on Future Simple or Passé Composé. 15 years later I do mange to communicate in both those languages to the level that people actually understand what I want to say and vise-versa. My Hollywood English off course is still better than my Bistro French but it took me 15 years to get here just through exercise and not by learning as such.