User Profile menu item - public and only one?

This is the main menu item of Community Builder. Please create only one of them and make sure that this menu item is of public access and published.

1. "Please create only one" - how is this supposed to work on a mutlilingual site?
2. "public access" - I dont want any guest seeing the members profiles. How is this gonna work with public access?

Profiles can still be set to be viewable only for registered members etc., independent of the menu item.
Not sure you'd need multiple menu items for multilingual sites. Make the menu item title a language string, then you can translate it to any language.

Make the menu item title a language string

Thanks, but that is not possible in Joomla.

1. "Please create only one" - how is this supposed to work on a mutlilingual site?

Create one for each language. Menu items can be assigned to a specific language and you'd simply create one for each. You don't have to create only one; multiple will work, but we always advise to keep as simple as possible to avoid any complications or configuration confusion.

2. "public access" - I dont want any guest seeing the members profiles. How is this gonna work with public access?

The profile menu item is used for its Itemid. It controls access of more than just the users profile. You for example could create a profile menu item and put it on a menu that'll never be displayed and leave it with public access so it can be used for its Itemid. You can then create menu items for your various languages.