i am using a code that was answered posted here and answered very well .

Prev/Next child navigation for current page? answered by user phife-dawz

the issue i am trying to run that inside a function by calling it inside a page template

<?php 
 if (  is_page(array('5145','7','8','25'))  ) {
    
 getPrevNext(); 

}
?>

and the function is placed inside the code snippet plugin
and it is this

function getPrevNext(){
$pagelist = get_pages("child_of=".$post->post_parent."&parent=".$post->post_parent."&sort_column=menu_order&sort_order=asc");
$pages = array();
    $pages = array();
    foreach ($pagelist as $page) {
       $pages[] += $page->ID;
    }

    $current = array_search($post->ID, $pages);
    $prevID = $pages[$current-1];
    $nextID = $pages[$current+1];
    
    echo '<div class="navigation">';
    
    if (!empty($prevID)) {
        echo '<div class="alignleft">';
        echo '<a href="';
        echo get_permalink($prevID);
        echo '"';
        echo 'title="';
        echo get_the_title($prevID); 
        echo'">Previous</a>';
        echo "</div>";
    }
    if (!empty($nextID)) {
        echo '<div class="alignright">';
        echo '<a href="';
        echo get_permalink($nextID);
        echo '"';
        echo 'title="';
        echo get_the_title($nextID); 
        echo'">Next</a>';
        echo "</div>";      
    }
}

****

the output i get is only showed with Next link , but that also shows only a specific next page regarding the page we are viewing