Hello sophie,
Add this code into custom.css file.
.main-nav .menu > li.menu-full-width .nav-sublist-dropdown .container > ul > li.et-col5 { margin-left: 0; }
Here is a video tutorial how to create custom.css: https://www.youtube.com/watch?v=Qok2zRedRMY&feature=youtu.be.
Regards, Robert Hall.
