Image in the hero and navigation sections

Hi,

does anyone know how to make sure the image in the mobile version takes up the whole space in the hero section? At the moment the image I added appears really small and stretched out, and it’s not professional.

Do you also know how to incorporate the image in the navigation as well? At the moment I have a grey band which looks quite odd.

Thank you!

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