Hi! I am still fairly new to WordPress and have an issue i’d like to fix.

I am using the theme “Ultra” if that makes a difference. There is a dark grey bar on the very top of the page. There is two different places to put menu links. On desktop you can either put menus on the top right or the top left. On mobile the same menu locations are stacked. One on top of the other. I only want to use one of the locations for links, but when I leave the other blank, On mobile, the bar thickness stays the same as if there were links there, so as a result, there is a empty bar above or below if I switch the location of the links.
How can I do this