Studio theme drop down & navigation problems

Hi:

My production site is here:

http://few.modernmediajapan.com/#

1. Dropdown problem
If I click Our Community, Instead of a completely black panel, the drop down is part black and partly takes on the background color of the page. I want it all to be black (please screenshot).

What should I do?

2. Navigation problem
The navigation buttons at the top seem to have moved to the header for some reason: I want them to be back where they were originally. I changed the header background to white, and I also uploaded a square logo, and then this happened. Not sure what to do.

btw, could you let me know where the css file is to make style changes? the Studio Child css file is pretty empty, and I'd be happy to cut and paste code into it from the parent Studio theme css, but this is all I see there:

/*

Theme Name: Studio
Theme Date: 20/09/2010
Version: 2.1.5
Theme URI: https://premium.wpmudev.org/
Description: Studio is a versatile business theme to advertise services or your portfolio in a modern elegant style
Author: Tammie Lister - WPMU DEV - The WordPress Experts
Author URI: https://premium.wpmudev.org
WDP ID: 155

Tags: buddypress, 2 columns, fixed width, threaded comments, theme options

Uses BP-Default theme files and styling for BuddyPress components with some customisation for theme.
Included in theme to allow for own child themes rather than being child of BP-Default

The CSS, XHTML and design is released under GPL:
http://www.opensource.org/licenses/gpl-license.php

*/

/* 9604-1325585485 */

So, does this mean that the CSS I need to edit is in the BuddyPress plugin folder? I'm confused. thanks,
Terri

Thanks.

btw,