skyfranky Hi
Kindly check as the specific section i.e. extensions --> templates --> templates isnt accessible and returning with error as shown in screenshot due to which unable to access custom.css file in order to edit the same
Other way, You may kindly add ftp details in edit fields or
1) Try add this to custom.css file and adjust width value accordingly :
.t3-topbar .topbar-right{float: right;width: 30% !important;}
2) Also, Try change the above CSS to :
.t3-mainnav,.navbar-default .navbar-nav > li{height:55px !important;min-height: 50px !important;}