[Steven Zahm]

@ Bene

re: Is this possible to do whit shortcodes or in PHP?

Yes, this is what I would recommend…

Put this it the top of the card.php / card-single.php files.

foreach ( $entry->getCategory() as $category ) {
    $categories[] = $category->slug;
}

The to display the field use:

if ( ! empty( $text ) && in_array( 'meta_key', $categories ) ) {
    echo '<p>' . esc_html( $text ) . '</p>';
}

You would change meta_key to the name you entered in the custom field. It will need to be exactly the same to work.

Hope that helps, let me know.