share content with specific users

I created a new wordpress, but I need help with creating a communication channel with my users.
Basically what I need is the be able to share info and documents (word, excel, pdf, images, etc) with specic users.
The content shared with that user should only be visible for that user and me (administrator), and the user should be able to upload files too.

Maybe I can accomplish that with pages or posts.
The idea could be something like this:
– I create the “user1”
– I create a post that only the “user1” can see.
– I give “user1” permision to add content to that post.

All the comunication between me(admin) and the users should be private. The post should only be visible to specific users. So users won’t even see the post tile of another user.

I’m sure something like this should be doable, but I don’t have idea where to start. I’m a designer and new to wordpress.

Anybody have an idea??