Add functionality in an Existing Joomla site

We do have a joomla based website.? On that site we will require to have the following functionality:? Upon approval of the user registration a private area for the user will be created. 1. User's will be able to upload and download files (large media files)? 2. Other users won't be able to see contents of another user (except administrators).? 3. Admin will view all the folders for the users and when click on the folder he can upload or download media files from that folder.? In summary, this is a file explorer kind of functionality required, with user visibility. Also, I will require assistance fixing minor design issues n the existing site.