WordPress Blog Template content-blog.php current post_id

I want to style the first element of the blog different and i need a possibility to find it in php. I used the coming expression, but it shows only the first element: $postID=$wp_query->current_post;
The post of this Variable is always 0.
Here my Code, i hope someone have a solution for me. I use the Astra Theme with a Child Theme… and its the content-blog.php

    <?php
/**
 * Template part for displaying posts.
 *
 * @link https://codex.wordpress.org/Template_Hierarchy
 *
 * @package Astra
 * @since 1.0.0
 */

?>
<?php astra_entry_before(); ?>
<?php
$postID=$wp_query->current_post;
$marginPosition = '';
if ($postID != 0 && !is_paged()) :
    if($postID % 2 == 0 || $postID % 3 == 0) {
        $marginPosition = 'left-margin';
    }
    if($postID % 3 == 0){
        $marginRightPosition = "no-right-margin";
    }
    if($postID % 4 == 0){
        $marginPosition = '';
    }
    if($postID % 5 == 0){
        $marginPosition = 'left-margin';
    }
endif;
    echo $postID;
?>
<article
<?php
        echo astra_attr(
            'article-blog',
            array(
                'id'    => 'post-' . get_the_id(),
                'class' => join( ' ', get_post_class() ).' '.$marginPosition. ' '.$marginRightPosition,
            )
        );
        ?>
>
    <div class="article-holder <?php if( $postID == 0 && !is_paged() ) : ?>firstarticle<?php else: ?>standard-article<?php endif; ?>">

        <?php if( $postID == 0 && !is_paged() ) : ?>
            <div class="left">
                <div class="featured-image">
                    <a href="<?php the_permalink();?>">
                    <?php the_post_thumbnail( 'featured-blog-size' ); ?>
                    </a>
                </div>
            </div>
            <div class="right">
                <div class="title"><h2><a href="<?php the_permalink();?>"><?php echo get_the_title( ); ?></a></h2></div>
                <div class="latest-banner"><span>latest article</span></div>
                <?php echo do_shortcode( '[molongui_author_box]' ); ?>

            </div>
        <?php else: ?>
        <div class="top">
            <div class="standard-image">
                <a href="<?php the_permalink();?>">
                    <?php the_post_thumbnail( 'standard-blog-size' ); ?>
                </a>
            </div>
        </div>
        <div class="bottom">
            <div class="title"><h2><a href="<?php the_permalink();?>"><?php echo get_the_title( ); ?></a></h2></div>
            <div class="written-by-content">
                <div class="right-wb">
                    <span>by <a href="#">Josephine Choo</a>, PhD<br></span>
                    <span>Consultant</span>
                    <div class="date"><?php echo get_the_date( 'F dS Y' ); ?></div>
                </div>
            </div>
        </div>
        <?php endif; ?>
    </div>
</article><!-- #post-## -->
<?php astra_entry_after(); ?>