Are you modifying the style.css file? Those changes will be lost when the theme is updated. You should be using Custom CSS or a child theme.
You also have a syntax error in the CSS you’ve added – a missing closing bracket here:
.navbar .nav li.dropdown.open > .dropdown-toggle,
.navbar .nav li.dropdown.active > .dropdown-toggle,
.navbar .nav li.dropdown.open.active > .dropdown-toggle {
background-color: #e5e5e5;
color: #349cd1;
/*make the menu sub-menu items drop down on mouse hover */
As to the fix, try this CSS:
header.tc-header {
border-bottom: 0 none;
height: 100px;
}
.navbar .navbar-inner {
margin-top: 0;
}
You’ll need to make the logo smaller.