创建新页面后无法获取ACF字段

We are developing a crowd-funding platform based on Wordpress' "advanced custom fields". In order to create a new funding-project we fill ACF-fields (in a HTML-form). On submitting we create a new WP-page:

$post = array(
        'post_name'      => $pname,
        'post_title'     => $pname,
        'post_type'      => 'page',
        'post_parent'    => 8,
        'page_template'  => 'project.php'
    );

$this->post_id = wp_insert_post($post); 

Strangely we cannot access the field variables with get_field(" ... ") before we manually click onto "Save" or "Publish" on the page in the Wordpress backend. wp_update_post() or wp_publish_post() make no difference.

Do you have any suggestions?

We just found the solution! Using the field key instead of the field name on filling the fields worked!