Ajax current language

Hi everyone,
I am trying to make some ajax working with Polylang and I have a problem with language.
It is always detected as default language and not the current language.
So I manage to force the language in $_POST[‘query_vars’] to find just posts of current language => orderby=date&order=DESC&lang=en&post_status=publish, but translations into loop-category.php are still in french, the default one => “Lire plus”
Any idea how to force/initialize polylang into the AJAX function with the current language of the user ?
Maybe it is because Ajax is rendered by admin-ajax.php and the language is not the same as frontend part ?

functions.php

function html5blank_header_scripts()
{
    // write variables into DOM
    global $wp_query;
    wp_localize_script( 'ajax-pagination', 'ajaxpagination', array(
        'ajaxurl' => admin_url( 'admin-ajax.php' ),
        'query_vars' => json_encode( $wp_query->query )
    ));
}

/*------------------------------------*\
	Ajax
\*------------------------------------*/
add_action( 'wp_ajax_nopriv_ajax_pagination', 'my_ajax_pagination' );
add_action( 'wp_ajax_ajax_pagination', 'my_ajax_pagination' );
function my_ajax_pagination() {
    var_dump(pll_current_language()); // always the default language (FR)
    $posts = new WP_Query( $_POST['query_vars'] ); // orderby=date&order=DESC&lang=en&post_status=publish so it loads only posts with lang=en...
    $results = array();
    $GLOBALS['wp_query'] = $posts;
    $results['html'] = load_template_part('loop', 'category'); // but the language into the render is stil the default one (FR)
    echo json_encode($results);

    die();
}
function load_template_part($template_name, $part_name=null) {
    ob_start();
    get_template_part($template_name, $part_name);
    $var = ob_get_contents();
    ob_end_clean();
    return $var;
}

loop-category.php

<?php while (have_posts()) : the_post(); ?>
<?php the_title(); // OK : EN language thanks to the WP_query &lang=en param ?>
<?php _e( 'Read more', 'html5blank' ); // KO : FR language => Lire plus ?>
<?php endwhile; ?>

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