It looks really good but there a few things that can make it look better.
The background color is a little too strong. I think simple colors such as white or a two-tone design like back-white do a better job.
The navbar is too big. If you want to make it fully responsive without giving it a width, here’s what you can do.
Put your navigation bar inside a div and do the same thing for your main (or header +
main + footer) content and give each div a class or id.
Put your navigation div and main div inside a general div and give it a class or an id.
give this div a display:flex, flex-direction:row, align-items: flex-start and
width:100%.
give your navigation flex-shrink:0, flex-grow:0 and some padding if you like.
give your main content div a min-width:0.
DONE.
As you’ll see, your main content and navbar will automatically fill the screen without giving any of them a predefined width, making your website look good on any device.