Hi Virginie,
The first discussion link is actually 'Conversations'(http://take.ms/4f2fl).
You can change the translation by using the language constant below in your language override section. Notice that currently you have conversation translated as discussion(http://take.ms/bUA9w).

COM_EASYSOCIAL_PROFILE_NOTIFICATION_TITLE_CONVERSATIONS="Discussions"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_REPLY="Nouvelle réponse dans la discussion"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_REPLY_DESC="Détermine si le site doit vous avertir quand une réponse est publiée dans une discussion à laquelle vous participez."

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_NEW="Nouvelle discussion"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_NEW_DESC="Détermine si le site doit vous avertir quand un utilisateur commence une discussion avec vous."

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_INVITE="Invitation à rejoindre une discussion"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_INVITE_DESC="Détermine si le site doit vous avertir quand vous êtes invité à vous joindre à une discussion."

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_INVITED="Nouvel invité dans la discussion"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_INVITED_DESC="Détermine si le site doit vous avertir quand d'autres personnes sont invitées dans une discussion à laquelle vous participez."

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_LEAVE="Un utilisateur quitte la discussion"

COM_EASYSOCIAL_PROFILE_NOTIFICATION_SETTINGS_CONVERSATIONS_LEAVE_DESC="Détermine si le site doit vous avertir quand une personne quitte une discussion à laquelle vous participez."

As for your discussion and group discuss notification, I check your alerts in the backend and I see this(http://take.ms/u94ho). I'm not sure why but it seems there isn't any value to those email and system state, which is why it is not configurable in the frontend.
I have helped you publish the email and system state for those alerts(http://take.ms/4cGl7) so you should be able to configure them in the frontend now.

Hi Raymond,

Thank's a lot.
Just one question: I use only group discussion. "Group discussion" notification system uses discussion notification ? Can I unpublish all discussion notifications ?

Hey Virginie,
Yes you can. All alerts can be managed in the alerts section in the backend. You are free to unpublish/publish any alerts as you desire. Do note that there are 2 types of notification, system and email. System notification is the one that notifies users in the notification icon in the toolbar whereas email notification notifies users via email.

Ok thank you !

Hey Virginie,

You are most welcome. Glad to hear that your issue has been resolved now.
I will lock and mark this thread as resolved.