get_locale() // returns the WordPress locale in the format 'en_US'
get_bloginfo('language') // returns the locale in the format 'en-US'

$posts = get_posts( array(
    'post_type' => 'post', // nebo custom co mas
    'lang' => 'cz', // tohle getne ty posty v jazyku v jakym potrebujes
    'showposts' => 5, // pocet posts
) );

if (false !== stripos($_SERVER['HTTP_REFERER'], "http://priklad.cz/de/")){
   wp_nav_menu( array(
    'menu' => 'menu_de'
) );
$logo_url = 'nemeckej home';
}