customizing the site header

Hi,

I have two issues I am trying to resolve.

1. Site Header:
I am struggling with the site header on the twenty seventeen theme. I want the navigation to appear at the top of the pages above the image of the couple. So instead of using a “header” image. I am setting the prominent image as a “featured” image. This moves the image below the navigation instead of above it. The problem is, that now when you scroll down, the navigation drops down and covers the top of the couples image. I can’t figure out how to remove this or change it.

2. When you click on the “wedding schedule” link at the top of the page, the dropdown background is white and the links are also white. I can’t find where to change the color of the links in the drop down menu.

website is:
https://sitesbysarah.com/jennandlucas/

Thanks for any help you can provide.
sarahb