How to edit mobile menu and hamburger icon

Hello all, I recently built this website. I posted this question in the general section and they advised me to post in this section due to this being a theme question.

I’m having a problem with the mobile menu. I cannot change the background color or the text color or the hamburger icon color/size. I have looked everywhere and I cannot find the code to edit or plugin to install. There is no option in any menu in the WP editor for the theme I’m on. I tried installing AMP and Elementor…..unable to find the setting. I’m at a loss. The desktop version is working correctly, it’s the mobile menu that’s not in line with the theme and difficult to read.

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