I have done all of that but I still getting this rectangle in my pages (see inside the red marker). Do you know how to remove it completely?

 

Thank you  ]

 

That area is styled by the K2.css and setup in the category_item.php
You can control some aspects of this within the k2 Category parameters, see this chapter for more information

Look under the category item view to disabled title and item count.

Regards,
Simon
K2joom.com
Supporting K2 & Joomla