In your stylesheet, you have the following CSS for ID #header-container around line 536:
#header-container { background-image: url(https://www.djshandyservices.com/wp-content/uploads/2014/11/DJS11801.jpg) ; background-repeat: no-repeat; background-position: top center; height: ; }
Try adding background-size: contain; within that style. That should resize your image based on the viewport size.
Just as a note, your stylesheet contains a lot of fixed-width styling, instead of percentages. This is causing the rest of your page to have scrollbars appear when changing the size of the viewport (window size) instead of scaling. In other words, the custom styling is not allowing your site to be responsive.
If you want some sidebar content (for example, your search area), try dragging a widget into the “Sidebar” widget area (Appearance>Widgets from your WP admin menu). Keep your main content in a page or post without trying to fix any sizes.
Hemingway is a responsive theme, but you only have main content, one sidebar position, and three footer positions to use.
If you want certain sidebar content to appear only on a certain page, try using the Dynamic Widgets plugin. It will allow you to do just that! ??
