Hi sonosergio
In the documentation of JA Megafilter, we have instruction for how to override: https://www.joomlart.com/documentation/joomla-component/ja-megafilter#override-layout
In this guide, it mentions override for Virtuemart plugin, you can apply the same for content plugin, you need to override 2 folders:
1 - Copy file plugins\jamegafilter\content\tmpl\default.php and paste it on folder templates{template_name}\html\plg_jamegafilter_content\
2 - Copy the folder plugins\jamegafilter\virtuemart\layouts\default\product-toolbar.php and paste it on folder templates{template_name}\html\layouts\jamegafilter\content\default\