You are paying for the classes, i.e. the attention and time of your teachers. Make sure to get your money's worth: if you don't understand something speak up, or contact the teacher after the class. If your class has teaching assistants contact them (for example by email) if you get stuck on the homework/exercises or don't understand something from the lecture. All of these people are literally being paid to answer these questions, be aware that this is a resource you have at your disposal at all times. A common failure mode is thinking: "It's embarrassing to speak up in front of the whole group and/or I don't want to waste their time, I'll just figure it out on my own later" - if you have this thought contact the teacher/assistant after the course about the part that wasn't clear.