Reducing height of menu bar when viewed in browser

Hi. Using evolution pro. I notice when the browser size is reduced, or the site viewed on mobile, the menu bar increases by approx 20 px in height which i'd prefer not to happen as it is too large on mobile screen. I've being trying for a few hours without success to change this, any way? I found it's controlled by padding in responsive.css but I can't work out how to control that in my child theme style.css