BTW when I go to cPanels ftp manager I can see public_html folder but I cannot go into
this folder. So I cannot delete a subfolder of public_html through cPanels ftp manager.
Unless it works differently than on a shared system, you need to click on the folder
icon,
not the "public_html"
name, to get to lower level directories. That, or someone really screwed up your public_html permissions.