older posts not showing

Hi, I’m trying to transform twenty thirteen into a custom template. First, I tried to custom an external static page but I Haven’t the full avantage. So I return to this template to have a custom and personal presentation in grid based with my code for the older external site, but when I’m using the pagination, I’ve got the same posts displayed. I know that’s the debut of my code which is wrong, but I don’t know how to change it. How can I do this ? Here is my code, thanks a lot :

<?php define( 'WP_USE_THEMES', false ); get_header(); ?>

	<div id="articles">
<?php
$compteur=0;
	echo '<div class="tableau">';
	echo '<div class="colonnes">';
$posts = get_posts('numberposts=10&order=DESC&orderby=post_date');
	foreach ($posts as $post)
{

setup_postdata( $post );
	echo '<div class="col">' . "\n";
 	echo '<div class="img-crop">';
 	if ( has_post_thumbnail() ) {
    echo '<a href='.post_permalink($ID).'>';
    $image_src = wp_get_attachment_image_src( get_post_thumbnail_id(),’thumbnail’ );
     echo '<img src="' . $image_src[0] . '">';
}
	echo '</a>';
	echo '</div>';
	echo '<br/>';
	echo '<div class="date">';
 	echo the_time('j F Y');
 	echo "</div>";
 	echo '<div class="title">';
	echo the_title();
	echo "</div>";
	echo '<div class="excerpt">';
	echo the_excerpt();
	echo "</div>";
	echo "</div>";

	$compteur++;

if ($compteur==3)
{
	echo "</div>";
	echo '<div class="colonnes">';
	$compteur=0;
}
}
	echo "</div /></div>" ;
?>
</div>
<?php twentythirteen_paging_nav(); ?>
<?php get_sidebar(); ?>
<?php get_footer(); ?>