Hi ninoparisi
Try with this
edit this file
/templates/ja_fit/tpls/blocks/header.php and change from
<header id="t3-header" class="container t3-header">
to :
<header id="t3-header" class="t3-header" data-spy="affix" data-offset-top="52">
Then add to your custom.css file in this folder /templates/ja-fit/css/
.t3-header.affix {
position: fixed;
top: 0;
z-index: 10000;
width:inherit;
background:#000;
}
@media (min-width: 992px) {
.affix .t3-mainnav {
top: 90px!important;
position: fixed;
width: 1600px;
max-width: 100%;
}
}
If you do not have a custom.css already then create a new one.
Regards