How to get next and previous post into ajax formed modal windows?

I solved this issue thanks to Tom J Nowell He gave me the right idea in his comment. Everything is really ease (but I didn’t think of it myself) in order to get the identifiers of the previous and next post, it is enough to include them into ajax request. This is how it looks:

<?php
   $post = get_post($post_id);
   $previous_post = get_previous_post();
   $next_post = get_next_post();
?>
<div data-next-id="<?php echo $next_post->ID; ?>" data-prev-id="<?php echo $previous_post->ID; ?>" data-new-id="<?php echo get_the_ID(); ?>" class="news-item">

In the post card, two attributes are created in which the ID of the previous and next post are passed.

Now slightly modified js code:

if(prevPost !== null){
    prevPost.addEventListener('click', function(){
        let prevAttribute = this.getAttribute('data-prev-id');
        $.ajax({
            type : 'POST',
            url : wp_helper.ajax_url,
            data : {
                postid : prevAttribute,
                action : 'loadprevpost',
            },
            success : function( data ){
                
                $('#exampleModal .modal-body').html(data);
                lazyLoad();
            }
        });
    })
}

And php function:

add_action( 'wp_ajax_loadprevpost', 'really_loadprevpost' );
add_action( 'wp_ajax_nopriv_loadprevpost', 'really_loadprevpost' );

function really_loadprevpost() {

$postid = $_POST[ 'postid' ];
$post   = get_post($postid );
setup_postdata( $post );

if (have_rows('news_content',$postid)) {
       
    echo'<div class="news-single">';
        while (have_rows('news_content',$postid)) : the_row();
            if (get_row_layout() == 'section_title'){
                
            /// Post data here
            
            }
            
        endwhile;
    echo'</div>';
}
 wp_reset_postdata();
  wp_die();
 }

Perhaps the solution is not elegant, but it works, for me this is the main thing now.