As always, talk with your advisor if you're not sure what to do about a course. During the withdrawal period you can leave a course by filling out the appropriate form. List the grades you have received on assignments, quizzes and exams. Take stock of how much you have learned from the course so far, and think about the time it's taken to aquire that knowledge. Determine whether spending more time on the course would help, and, if so, think about whether you have the extra tme to devote to the course.
Most courses are cumulative, as one topic builds upon the last.
Explore how much will the things you didn't learn in the beginning of the course will affect your understanding of the topics which will be discussed later in the course. If you decide you need to withdrawal, you first should talk with your professor about your standing in the course. Thus, your performance is often measured relative to the performance of the other students in the course. So, if your raw score on an exam is poor, that doesn't necessarily mean that your letter grade will be poor also. It would be best to make sure.