Restrict the amount of categories in mega menu and reorder it

I have a necessity to dig into my WP template and apply some changes. I've bought it by GPL license, so kind of unable to get direct support from the author, so here is the question: What I've got now: mega menu with which output all existing child categories originally sorted by name. What's needs to be done: mega menu which output specific amount of child categories sorted by the number of posts. I successfully solved the problem with the amount of categories here:

public function build_subcat_menu( $category ) {
    $subcat_output = $subcat_li = '';
    $children      = get_categories( [ 'parent' => $category ] );

    if ( ! empty( $children ) ) {
                
        foreach ( $children as $child ) {
            $subcat_li .= "<li data-cat-id=\"{$child->term_id}\" class=\"\"><a href=\"" . get_category_link( $child->term_id ) . "\">{$child->name}</a></li>";
        }

        $subcat_output =
            "<div class=\"jeg_newsfeed_subcat\">
                <ul class=\"jeg_subcat_item\">
                    <li data-cat-id=\"{$category}\" class=\"active\"><a href=\"" . get_category_link( $category ) . '">' . jnews_return_translation( 'All', 'jnews', 'all' ) . "</a></li>
                    {$subcat_li}
                </ul>
            </div>";
    }

    return $subcat_output;
}

By adding custom variable that checks amount of terms:

$i = 0;
foreach ( $children as $child ) {
$i++;
if($i > 8) {
    break;
}

But I still don't know what to do with its sorting. I expected to see something like:

$args = array(
    'orderby' => 'name',
    'order' => 'DESC',
    'hide_empty' => 1,
);  

And change orderby to "count" which would solve the issue, but it's not the case: the following code doesn't contain any array:

public function mega_menu_category_1_article() {
    if ( isset( $_POST['cat_id'] ) ) {
        if ( ( SCRIPT_DEBUG || get_theme_mod( 'jnews_load_necessary_asset', false ) ) && ! is_user_logged_in() ) {
            $frontend_assets = \JNews\Asset\FrontendAsset::getInstance();
            $frontend_assets->load_style();
            $frontend_assets->load_script();
            wp_print_styles( 'jnews-global-slider' );
            wp_print_scripts( 'tiny-slider-noconflict' );
        }
        $category = (int) sanitize_text_field( $_POST['cat_id'] );
        if ( is_int( $category ) ) {
            $article =
                '<div data-cat-id="' . esc_attr( $category ) . '" data-load-status="loaded" class="jeg_newsfeed_container with_subcat">
                    <div class="newsfeed_carousel">
                        ' . self::build_article_category_1( $category, (int) sanitize_text_field( $_REQUEST['number'] ) ) . '
                    </div>
                </div>';

            echo jnews_sanitize_output( $article );
        }
    }
    exit;
}

Since I'm not good at coding, could I please get some advices like "you get the X code, you need to paste/change it here".

source https://stackoverflow.com/questions/70643811/restrict-the-amount-of-categories-in-mega-menu-and-reorder-it