HI magnytu2
You can follow this guide for how to create sticky menu in a template built with T3 framework: http://www.t3-framework.org/documentation/menu-system.html#sticky-menu
JA Good uses a special header block, you can use my tweak here:
1 - Go to file: /templates/ja_good/tpls/blocks/header/header_news.php ( I suppose that you're using News style of this template)
2 - Edit the same as above guideline:
<nav id="t3-mainnav" class="wrap navbar navbar-default t3-mainnav" data-spy="affix" data-offset-top="70">
3 - Open this file: /templates/ja_good/css/custom.css (Create this file if it doesn't exist)
and add this custom css code:
.t3-mainnav.affix {
position: fixed !important;
top: 0;
z-index: 999;
}