This works in the GeneratePress theme to reduce excessive space at the top of pages.
/* Reduce height of the main content wrapper / .inside-article { padding-top: 0px !important; margin-top: 0px !important; } / Reduce height of menu */
.main-navigation .main-nav ul li a {
padding-top: 10px;
padding-bottom: 10px;
line-height: 20px;
}