=== UPDATE ===

In your case problem is becuase there is extra Module column after Menu column that is NOT used, but still take place also on smaller screen. And Menu column width is too small.

Method 1: If you used Custom Header - please change Grid. And keep only two columns (Logo +Menu), and change Menu column width from settings, make it wider.

Method 2:

Eventually this simple & lazy trick (Custom CSS) will help:

@media (min-width: 992px) {
#sp-menu {width: 65%;}
}