Coursepress alters my CSS settings

Hi there, when I install and activate CoursePress, it changes the CSS settings (I think so) of the template which I am using.

Can you please guide me, how I can stop this?

The menu items become squashed and the overall page area becomes squeezed towards the left.

Before activating CoursePress:
Here is the menu item before activating CoursePress:
Other elements:

Here is what happens once I activate CoursePress:
Other elements: