Hello!

the first thing to do is create your contacts through the Joomla! standard component. Create categories, create contacts with all relevant information.

Once done, you will be able to create your directory. You do that by creating a menu item called 'Trombinoscope'.
For that part, it will be much easier for you to download the documentation which explains everything in detail with screenshots and examples.

Let me know if you have any specific question or something is unclear in the documentation!

The problem is: I don't know what you want the gallery to look like

Right now, you already have created a gallery yourself, it is just a matter of selecting what you want to show.

If you want to show pictures for each contact, you will have to add a picture in the Joomla contact component. Otherwise, just show a default image.

You are welcome!