Theme -Openstrap

I have tried out a number of themes experimenting with Headers and this was the only theme that seemed to allow it with ease but since I added it I can’t figure out how to move the nav bar down. I have tried removing it all together but it just seems to remove the style and leave a unstyled nav bar or a gray box behind. Also If possible I would like to fill the space between the slides and the egdge of the slider box??is this possible?

the site is http://commercialsparesct.co.za/