How to show value from ACF plugin field in e-mail?

It was the thing in the order of functions, and the check :

 if(is_user_logged_in()){
        $current_user = wp_get_current_user();
    }
    else {
        $user_id = get_post_field( 'post_author', $post_id );
        $current_user = get_userdata($user_id);
    }