got it (it is explained here: http://www.advancedcustomfields.com/resources/how-to/how-to-query-posts-filtered-by-custom-field-values/ and here is the user_query explained: http://codex.wordpress.org/Class_Reference/WP_User_Query):
<?php
// args
$args = array(
'meta_query' => array(
'relation' => 'OR',
array(
'key' => 'country',
'value' => 'germany',
'compare' => 'LIKE'
)
)
);
// The Query
$user_query = new WP_User_Query( $args );
// User Loop
if ( ! empty( $user_query->results ) ) {
foreach ( $user_query->results as $user ) {
echo '<p>' . $user->display_name . '</p>';
}
} else {
echo 'No users found.';
}
?>
<?php
// aaaaaand reset ...
wp_reset_query();
?>
