Need a new Web site built from a failing site

I have a site that was started and does some things well but other things are not working well at all. I need someone who can either fix what is broken, or rebuild a better site for me. The site features a public area and private area, with CMS so I can change the content. But I need to be able to add images and files that members can download and I can't do this write now. I also need to be able to add advertisements and affiliate links, and can't right now. The site also has a custom database with contact/address book info, and other company info and I need to be able to access this better from the front and back end. As the Admin, I need the ability to easily login as any user and add/change content. I can't do this easily now and I know there has to be an easier way. I need to be able to easily add promotions, coupons, links, etc. I need to be able to manage members better too. If you speak good english, and can seriously help, please bid on this, and explain how you can help. If you send a generic bid, I will not consider you. If you have questions, ask away. If you can show samples, please do. Ask to see the site and I'll PM you with the link. The technology the site currently uses is PHP and MySQL on a Linux. Thanks!