Remove container line

Also, just adding to my previous post, how can I add a thin colored line right below the navigation?

The goal of this is to separate the navigation from the rest of the content, similarly to how https://www.fool.com/ does it

Hi there,

1. Go to Customizer > Additional CSS - remove this:

.inside-article,
.sidebar .widget,
.comments-area {
    border: 1px solid rgba(232, 234, 237, 1);
    box-shadow: 0 0 10px rgba(232, 234, 237, 0.5);
}

Simple line below nav:

.main-navigation {
    border-bottom: 2px solid #f00;
}

Excellent, thanks!

you're welcome