All my friends say they did poorly in calculus and that it's difficult. Is that true?
That depends on what you define as hard. If you mean the material is abstract and requires much mental energy towards acquiring the material then, yes, this class is difficult. The material requires your attention and a certain amount of dedication. It also depends on your background in mathematics. However, with solid algebra skills, proper studying, and effort you will do well. That's all there is to it.