How to create an Intranet with WordPress

Hello folks,
I have a problem.

The Website is for a company offering a service. After cliking on buy now, I want there information to be stored in a secured part of the website (Intranet for the employees, maybe with user rolls only a certain group of employees may see it). Within this part of the intranet there should be a way to communicate, like chat, messaging, preferable integration of openoffice, to work on files online!

Furthermore I need another Intranet or Community, where Clients can talk to each other. Every would have a profile, with picture, email, social accounts and some more information.

So my hope was to have all these within one wordpress installation, to make it easier. So can you recomment any kind of plugin for that purpose? But I guess it will be better to have both Intranets to be kept seperated for security reasons. So I figure I could have three wordpress installations.

WordPress 1 would be the website
Wordpress 2 (located in https://www.domain.com/intranet-employees/) would be for employees
Wordpress 3 (located in https://www.domain.com/intranet-clients/) would be for our clients

Is there any other way I can do that?

Or should I install an other opensource software instead of WordPress 2 and 3? But is there a free intranet version?

thank you!