College is not meant to be hard and there will be classes that you know nothing about. The goal of a course is for you to learn. If you simply can not grasp the topic that is being discussed in class, you can ALWAYS get help. Campuses offer a lot of help like tutoring or even going to the professor for help on assignments.
There may come a point where even help can not even help you learn what the course is about. At that point, your best bet would be to withdraw from the course. A lot of students struggle with coming to the concept that they may have to do this. To help myself, I made a list that consisted of pros and cons.
The list of cons, although very short, consisted of: having to take another course that would make up for the missing credits, and the people in my class knowing that I quit.
I eliminated that last con with my list of pros: having more time on my hand to focus on my other classes, I would still be a full time student, an online class may be easier for me to learn in, it is better to have a W on my transcript instead of an F, and failing could seriously drop my GPA.
Now that I have withdrawn from the course that was taking so much of my time, I finally feel free and am doing better in my other courses. To conclude, it is never wrong to withdraw from a course and there are many reasons why it is not wrong. If you feel as though you are struggling, do what you need to do for yourself.