Hello Napiza,
It is possible to change the categories layout look and feel but you may have to do some changes to this file located in your local joomla folder as shown below
your_local_Joomla_folder\components\com_easydiscuss\themes\flatt\categories.php. Be sure to do a backup of the file described before you make any changes, this is to ensure when anything goes wrong you may revert back to the original look and feel.
Hope that answers your question
Regards
Kheng Wei