responsive

@sanderbloem, I checked the site linked to your username, and it appears you have gotten this taken care of as the menu is not floating over the header image, but right at the top of the featured content slider images.

Ah, I’m seeing what you mean on the site you reference. There are two options.
1. Remove the following from your child theme CSS:

.main-navigation {
    max-width: 40%;
}

2. Enclose the above in a media query to limit it to when the full menu shows, like this:

@media screen and (min-width: 886px) {
.main-navigation {
    max-width: 40%;
}
}

I would think the second would be the best solution.