Size and/or color

Sorry for bad english

Hello ladies and gentlemen, I need help please.

I can't get the logo to fit in the white space, its like white has to be arround it no matter what size of logo.

Idea 1: Is there anyway to change the white background to another color? If so where do i go theme files and wich?

Idea 2: can I change dimensions to allow image to take up whole top bar?

Image:

THANKS!!!