Welcome to cycling! One thing that will help you with maneuvering, cornering, etc. is to relax. When I first started mountain biking, I was really tense at times, to the point where I actually overshot the trail with too wide turns. So how do you relax when you're new and nervous? Well, the main thing is to just get out and ride. The more you ride, the more confident you will be, and just like your teacher always said, "Practice makes perfect!" That being said, I find that certain things still make me tense up, and I have to remind myself to relax my muscles. And for some reason, hard right turns (but not left) on single track challenge me. Maybe you could try getting out for rides when there are fewer people around? That's what worked for me.