well, community medicine is a
very important subject in 4th year it comes right after medicine in importance (even before surgery!!!).
It's like you described it as cocktail of many medical studies, all summed together.
They usually take systems one by one and talk about their diseases and the prevention and control of those diseases (the most important thing in those lectures).
You might see it as a mess, but the question are somehow predictible, you can find out when you're studying what is the important from a community medicine point of view, and focus on that

Take good care of it, it's really important in your marks, like I said, comes before surgery!
If you have any further question don't hesitate to ask