Hello,
You're right — the GCK Store template is quite outdated now. You may want to consider switching to another template that’s already compatible with Joomla 5:
👉 Joomla 5 Compatibility Status: https://www.joomlart.com/joomla-status/index.php?group=gavick
However, if you’d like to continue using the GCK Store template on Joomla 5 or Joomla 6, our Custom Services team can help make it compatible for you.
Best regards,
Heinz