[Theme: Hemingway Rewritten] Header and Menu Problems on Mobile

Hi, I figured out how to customize my header and main navigation using CSS but am having difficulty with these elements on mobile devices.
1) My site title/header is partially chopped off on mobile devices.
2) My main navigation menu is not showing up at all on mobile devices. When I click on where it should be, the menu options appear with a dark gray background. I would like the menu to be a white background with black font.
The website I would like help with is https://www.gratefulgrazer.com
Thanks!