SQL query optimized - Website Performance issues

General information for the website: Online Directory
Kind of development: Customization of existing website
Description of requirements/features: Hi

We are having issues with some webpages loading slowing and need someone to fix these issues. The problem is when we have a large number of entries associated with a specific category.

The below page has over 1100 entries associated with the category Clothes Shops Womens and is taking a long time for the page to load

http://www.shoppingonline.ie/category/clothes-shops-womens

The below page that has only 14 entries associated with the category loads quickly.

http://www.shoppingonline.ie/category/butchers

We are using the latest version of Joomla. 3.6.5 and J directory component

https://extensions.joomla.org/extension/j-businessdirectory/

We are using MYSQL verison 5.5.52

Kind Regards

Scott
Specific technologies required: Joomla, PHP. MySQL
Extra notes: