Project not readable by admins
Is it possible to start a project, where all the messages, tasks, etc would be not visible, readable to admin? Just for the creator and users. Thank you.
Admins have all permissions in all projects. With Redmine's permisison system, It is not possible to restrict admins from anything by design.
You you want users to only have access to their own projects, you need to remove the admin flag from those users.