I'll answer in English and not in French because I'm transferring your issue to the user mailing list where the community could help you. You can find more information about how to have support: https://www.qubes-os.org/support/. More recently it's not a "discord" but a "discourse" forum https://forum.qubes-os.org/ where you can post your request too.
Looking briefly to your issue, it seems that your dom0 (XFCE?) window manager might has its config broken. As a first attempt, I would try to clean the XFCE configuration by deleting/moving the folder in your dom0 user ~/.conf/xfce4. I would also ensure having latest updates: "[XXX@dom0 ~]$ sudo qubes-dom0-update"
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