finally got it:`
<?php $attachment_id = get_field('download');
$url = wp_get_attachment_url( $attachment_id );
$title = get_the_title( $attachment_id );
// part where to get the filesize
$filesize = filesize( get_attached_file( $attachment_id ) );
$filesize = size_format($filesize, 2);
// show custom field
if (get_field('download')): ?>
<a href=”<?php echo $url; ?>” ><?php echo $title; ?></a>
<!– show filesize –>
<?php echo $filesize; ?>
<?php endif; ?>
`
🙂 <- happy
