Try to add the rules below in Main options > Fonts & Custom > Custom CSS Rule box. You can tweak the values to your liking.
It looks like it works, but test and post back if it needs more work
.is-desktop .wvrx-menu ul {left:-180px;}
.is-desktop .wvrx-menu ul li {display:inline-block;}
.is-desktop .sub-menu .sub-menu {left:-150px;top:30px;}