Hey, I am a bit confused at this point on what I should learn/when I should learn it

.
What I mean is that my college I'll be going to has Visual Basic
ONLY as a class... As far as knowledge for VB, I have just enough to print a label change some text and add some text. I know most of the interface and some of the special commands, but no real special amazing stuff... Is this enough? I mean, it is only 2 classes and it is just for my AA. I want to be as ready as possible since I don't know how good at programming I am, and don't wanna get left behind from the other people (not to mention I'm 16 and going to be taking classes that 19-20 year olds have problems with).
But here is my problem, I am not interested in Visual Basic

. I am interested in C/C++, in fact I've already started reading books/doing tutorials for C. But I am afraid that if I spend all my time on C, I won't be prepared enough to even finish my vb classes X_X. Should I be worried about that? More importantly, how hard are those classes typically? Also, if possible I'd like to know at what point I will probably know when I'm done

. I'd rather have learn it whenever I want stuff right now than have to be stressed and work hard in class

. I know I am a nervous and anxious kid but I HATE not knowing and hate not being ready X_X.