Warning: count(): Parameter must be an array or an object that implements Countable in /home/pakhomec/public_html/oc-content/plugins/success/index.php on line 35

Warning: Cannot modify header information - headers already sent by (output started at /home/pakhomec/public_html/oc-includes/osclass/utils.php:2286) in /home/pakhomec/public_html/oc-includes/osclass/utils.php on line 2291








Warning: count(): Parameter must be an array or an object that implements Countable in /home/pakhomec/public_html/oc-content/plugins/success/index.php on line 35

You should have this on index.php line 35:
  if(is_array($messages) && !empty($messages) && count($messages) > 0) {

If no, update.

mean i have to remove that line and replace with that code

Well, just update plugin before writing any kind of issue with it.

its updated version now error not showing
but still success box not showing

Then it's not configured or you have another issue there.
Create support ticket.