Center Primary top menu

Hi
I tried to center top menu but so far no luck, will appreciate any help, below is actual code,
many thanks
Aida

https://www.persianbritadventures.com/en/

#menu-primary {
font-size: 1em;
width: 100%;
margin: 0 0 10px 0;
float: left;
clear: left;
position: relative;
z-index: 99;
}
#menu-primary li {
display:block;
float: left;
min-height: 30px;
padding-left: 1.8em;
background: url(images/menu-separator.png) no-repeat left 15%;
}
#menu-primary li:first-child {
padding-left: 0;
background: none;
}
#menu-primary li a {
font-family: ‘Abel’, ‘Helvetica Neue’, Helvetica, Arial, sans-serif;
font-size: 1.333333333333333em;
font-weight: 400;
line-height: 1em;
margin-right: 1em;
display: block;
text-transform: lowercase;
}
#menu-primary li.current-menu-item a { color: #aaa; }
#menu-primary li li, #menu-primary li li.current-menu-item li {
clear: both;
float: none;
border-top: 1px solid #ddd;
padding-left: 0;
background: none;
}
#menu-primary li li:first-child, #menu-primary li li.current-menu-item li:first-child { border-top: none; }
#menu-primary li li a, #menu-primary li li.current-menu-item li a {
font-size: 1.166666666666667em; /* 14 / 12 = 1.166666666666667 */
text-transform: none;
color: #888;
margin: 0 5px;
padding: 12px 15px;
}
#menu-primary ul li a:hover, #menu-primary li ul li a:hover {
color: #222;
border-bottom: none;
}