Hello Mauro,
You will need to have a child theme because what you are trying to accomplish requires a template customization, we would highly to suggest that you use it. This allows you to make code changes that won’t be overwritten when an X update is released.
After the child theme is set up, you will need to copy the file wp-content/themes/x/framework/views/{your stack}/content-portfolio.php
and upload this file to your child theme’s folder in wp-content/themes/x-child/framework/views/{your stack}/content-portfolio.php
. And please do not forget your modifications into the file as well.
Be sure to {your stack}
with the current stack that you are using in your site. You can find it out in X > Theme Options > Stack.
Hope this helps.