Hi haonas,
You can use the following CSS Code:
.nav-item.has-icon i {
top: 33%;
}
.t4-megamenu>.navbar-nav>li>a, .t4-megamenu>.navbar-nav>li>.nav-link {
padding: 13px 0;
}
.t4-megamenu.animate.flipping .dropdown.show.animating>.dropdown-menu {
margin-top: 6px;
}