thanks all,
i looked at [SOLVED] Error updating system (error: GPGME error: No data) / Newbie Corner / Arch Linux Forums
i did sudo rm -R /var/lib/pacman/sync
then sudo -E pacman -Syu
great improvement
thanks for having provided me the entry points
i have still some strange ignored packages, that i would like to remove.
I will investigate with the links you provide me and let you know
thanks again 