Problems with Benevolence theme

I’ve just installed WordPress and picked the “Benevolence” theme to start with.

I added a 2nd sidebar and a horizontal nav bar, but I must have done something wrong with the codes because I got a horizontal scrollbar at the bottom of the page that I just can’t get rid of. o_O

I’d be very grateful if someone could help me find the error(s) in the code.

Thank you very much in advance.