To my embarrassment I found myself run into more troubles.
I resized Mageia partition (sda5) trying to make room for another distro (Ubuntu, which I aborted after waiting for too long )
The situation got worse. Mageia 7 starts but do not reach the login screen remaining with one "ball" stalled on the flash screen .
I run the "rescue" from Mageia ISO DVD, and could see all my files on the disk.
But I got the message " bootloader not found" (error 2 if I remember correctly) trying to rewrite the bootloader.
Need the forum's help
JJF