While biology is a challenging major, schools do offer support services for students. Some classes may be more challenging than others. In addition to the lecture, there is usually also a weekly lab. I would highly recommend using the support services from day 1.
The short answer is yes.
Studying biology is hard. You have to have a fundamental understanding of chemistry, physics, and biology to finish your degree. There are classes that almost everyone struggles with (mine was biochemistry) and there are classes that make people decide to study something else all together (Organic Chemistry II).
If you love biology and can see yourself doing it for the next 20-30 years, it is well worth it though. If you are the type of person that has more questions than answers and is interested in the minutia of biology, it really is a lot of fun too.