Problem with subpage

I created a second page, where you do not know how to remove what is in the picture attached, marked in red.
I just want to see the rest.
Help me please.

This is mainbody container, only on frontpage you can disable mainbody via template settings on other pages menu item have to be set to some type (like single article) so it is the place where you article should be displayed.

thank you very much