I just took a look at your website and there is an error in dashboard about the SMTP settings:
ERREUR D’ENVOI D’E-MAIL : L’extension WP Mail SMTP v1.9.0 a enregistré cette erreur lors de sa dernière tentative d’envoi
That's the issue that emails don't go.
Do you mean the vehicle per page on your dashboard page. There the post per page do not work. It show by default 10. To change the number of vehicles per page go to Dashboard -> Cars -> autoRoyal Settings -> and there you will have "Vehicles per page" field.