GeneratePress Peak Theme

I am trying to create a website with Beaver Builder using the “Peak” theme. There is a black rectangle at the top containing the words “Reach the Peak” and a call-to-action button. I would like to replace the black background with a photo, and edit the content, including eliminating the call-to-action button. I have tried the Customizer, and when I try to edit the page using Beaver Builder, the black rectangle disappears.
How do I do what I want?

The page I need help with: [log in to see the link]