I've created a project with Visible by following customers setting.

If I then create user with group Project/User or Project/Manager they can see all projects. Not only projects that they are assigned to as followers.

I tried turn off these two rules (clicked on button on the top right ):

But it didn't help and users or managers still can view all the projects.

I’ve got the task to make a platform for our customers where they can track project progress, file service requests, talk about issues etc. and we picked this Project addon. I would like to make some projects completely separate from the rest of Odoo and accessible for people from outside (preferably grouped into their corresponding company).

I’m completely new to Odoo. Although we are using it in our company I was never the person to configure it. At the moment we are using Odoo 8 daily but I have to make this platform on Odoo version 12. Also we have plans to migrate our Odoo to newer version (but first we want to launch only this platform).