ACF update_field() with post_type Relationship

Question

I have setup a wp multisite where you have the option to transfer a post from one site to another. All taxonomies and fields should be transferred too. Now I'm stuck on the part where I have to link the Author field (which is a custom post_type) that is a Relationship.

register_extended_field_group([
    'title' => __('News', 'janes-admin'),
    'key' => 'group_scope_news',
    'location' => [
        Location::where('post_type', 'post')
    ],
    'fields' => [
        Relationship::make(__('Authors', 'janes-admin'), 'authors')
            ->postTypes(['employee']),
    ],
    'style' => 'box',
]);

I can retrieve the $fields and then loop over them and insert them with the update_field() function

 if (!empty($fields)) {
    foreach ($fields as $field => $value) {
       update_field($field, $value, $new_translation_id);
    }
}

This works for all the basic fields but it won't add the Authors. I'm guessing I should insert these authors seperately but not sure about that.