Remove a post used in a page from the loop

You should use the query_posts() function and set the “exclude” parameter to exclude the posts you’ve already displayed. That would look something like:

<?php
query_posts( array( 'exclude' => array( $first_post_id, $second_post_id, $third_post_id ) ) );
?>

In the code above, the $first_post_id, $second_post_id and $third_post_id variables should be the IDs of the posts you need to exclude.

ok, but if i post a new article under one of the three categories obviously the post id will change. There is a generic way to esclude this three last posts?

https://codex.www.ads-software.com/The_Loop#Multiple_Loops_in_Action

particularly, the ‘array’ method of not duplicating posts;
after this heading ‘Note for Multiple Posts in the First Category’

i noticed that my theme use this code to hide the post in the slider:
<?php // Exclude the 5 featured posts from the loop for SEO purposes

$exclude = get_option('mx_exclude_featured_posts');
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$args = array('post__not_in' => $exclude, 'paged'=> $paged );
query_posts($args);
?>

Can i reuse that for my purpose?

You could certainly use something similar, but you’d need to build your own $exclude variable. You could make the $exclude variable an array, and add each of the $post->ID properties from your featured posts into it.

I have no clue on how build the array, any hint?
I should place the code after the loop?

It should remove the 3 posts featured in the boxes (libri, news, extra) from the loop beneath. See link https://bit.ly/e85eWC