It might be intimidating to ask for help in a lecture hall of hundreds of students. However, you should know that if you are having problems in a class, most likely many other students are as well. When you ask for help from a professor or a classmate, this is a normal process and it is how we learn and learn to work together. You can then find a "study buddy" whereby you take notes together, and study together. This is way more effective than trying to do it on your own.