You need to make some choices, as making it auto responsive by scaling the size of logo, button, hamburger, could be a bit of a car crash.
For example, try adding this CSS:
nav .navigation-branding {
margin-left: 0;
margin-right: 10px !important;
}
.navigation-branding img.is-logo-image {
height: auto;
width: 100%;
max-width: 184px;
}
.navigation-branding {
flex: 1 1 0;
}
This will make it so the Logo will adjust its size to accommodate the other items on smaller screens.
And then so as the Logo doesn’t do all the work, you can use this to reduce the CTA button font size on small screens:
@media(max-width: 420px) {
nav .cta-button {
font-size: 12px !important;
}
}