How to create a personal account for clients?

Question

CMS

Good afternoon.
I ask you to suggest any ready-made solutions for creating a personal account for clients of a start-up outsourcing company.
Approximately the following structure:
The main functions are the exchange and storage of pdf, ford, jeep and personal messages between the client and the manager.
The client must see the files that the manager sent him and upload his own files to send to the manager. (some kind of file manager), and private messages.
The manager should see a list of clients, by selecting someone from the list, file sharing with the selected client and messages should be displayed.