Help with CSS and Editing Header

Here’s my website: websterlightgrant.com
My theme is Vantage – SiteOrigin

I’m having trouble getting rid of the white space above my header.
I’ve been editing the spacing and padding however everytime I update the edit the change doesn’t apply.

Furthermore I would like to change the hover color from the default teal blue to a deep green.
I’m not sure which .hover code to edit.
I am in need of some guidance!!

Thank you!