CMS for existing website

Take a look at [login to view URL], I'm looking for a complete CMS for this site. The site has got many different sub sections, such as business, sport, history, banking, health, shopping etc. When user logs on they can then click on a sub section from a list. User will have a different password for sub section. From here the user can edit the page and add more pages to that sub section. I need this done as soon as possible, no time wasters please. Administrator will have full access to every section of the CMS. Only administrator can add more sub sections. Administrator should be able to edit menu on the left. Menu should be one file called by the rest of the pages on the site. When change is made to menu it will change on every page on the site. I would like suggestions for complete new main page. A page that can be updated with simple content every week. The site is already developed so shouldn't take long to develop CMS The winner must accept any extra changes i require during development of CMS. thankyou