https://www.casimages.com/i/190128102603787010.png.html

Sorry, but I don't know any Ossn page with an option to deliver private or public messages.
Please provide a screenshot.

no no we do not understand, when we write a message we can choose if the message is in private or in public, but it is in public by default, I would like to put it in private by default.

Maybe I'm not getting the point ... because even without 'Private Network' being installed I can't find a way to retrieve private conversations of other members.
So please provide more details about which way you're able to do that.

Thank you for your answer, I talked about the private mode for messages.

See following : https://www.opensource-socialnetwork.org/discussion/view/3280/ossn-totaly-open-for-non-logged-in-users

You need to enable Private Network component.