I did a bit of French in high school, then when I was 19 I went and stayed with a French family for three months. Prior to my leaving, I did one semester of night classes, but when I arrived I found they weren’t much use. Nothing can really prepare you for suddenly being surrounded by a new language. It was awful at first, so isolating and frustrating. The family I stayed with were extremely supportive, however, and spoke to me in French as much as possible. They patiently waited while I struggled to find the words during conversations, and gently corrected me when I made mistakes. In the evenings I studied, copying out verb conjugations over and over. In the mornings I listened to France Info, a radio station that repeats the same news report every 20 minutes or so. I avoided the company of English speakers and spent as much time with my host family as possible.
After the three months was up, I was fluent. I took an exam called the A level, which is High School equivalent in the U.S. I believe, and I achieved an A grade. To this day, though I don’t practice regularly, I can speak, read and write in French. I can get by in most social situations, but would probably come across as a blithering idiot in a formal setting. I have read several novels in French (with the help of a dictionary) and can just about follow a film.
Although I learned French under a set of unique circumstances, I will say that spending time in a French-speaking environment will improve your understanding and knowledge of the language tenfold, and speed up your learning. Having a native speaker as a teacher is one way of doing this, and could easily be arranged no doubt.
Confidence is key to learning a language, and if you’re timid about trying out the things you learn, this will inevitably hold you back. Being scared to try is one the hardest things I had to overcome as a language learner.