OK, it works!!!
Instead of using a Ventoy live usb, I used an BelenaEtcher live sub (from jlb, zorinos.fr). And it's ok, I have une access to my files on the PC 
I can open a terminal in my PC but with the live usb account :).
Right now, I am saving my data !
First save your datas...then we can look how full your disk is and edit /etc/default/grub.
Hello, thank you for your time and interest
Now it works, but I think I have an issue.
I have transferred all my personal data (Documents, video...) on my External drive.
I note that the system takes now... 230 GB out of 250 GB !!! Is it normal?
I have had some troubles with recent updates.
I wonder if this update has duplicated some system data!
I am considering to reinstall my system :).
Have a nice day.
José, France
Time Shift is the source of all this problem
Timeshift has run a backup on my PC...
and has taken 111 GB of space !!!
And that as blocked my PC!!!
OK
You can delete all old timeshift snapshots and only keep one or two. Also change the settings that not so many snapshots are kept and perhaps not so often are taken. Perhaps you can limit the space for snapshots, but I am not sure. Best would be to save snapshots on a separate partition or even better on an external device.
Everything is ok, except... Thunderbird!
Unable to run Thunderbird (from the desktop, the general menu and terminal)
No error message, just the pointer become a timer.
After 5 seconds, it becomes again an arrow.
Linked to the profile???
jrd10@jrd10-G3-3500:~$ find $HOME -name profiles.ini -print
/home/jrd10/snap/firefox/common/.mozilla/firefox/profiles.ini
/home/jrd10/snap/thunderbird/Archive/common/.thunderbird/profiles.ini
/home/jrd10/snap/thunderbird/common/.thunderbird/profiles.ini
/home/jrd10/.mozilla/firefox/profiles.ini
/home/jrd10/.mozilla/firefox-trunk/profiles.ini
/home/jrd10/.mozilla/firefox-esr/profiles.ini
/home/jrd10/.local/share/QGIS/QGIS3/profiles/profiles.ini
/home/jrd10/.thunderbird/profiles.ini
/home/jrd10/.var/app/org.mozilla.firefox/.mozilla/firefox/profiles.ini
/home/jrd10/.var/app/one.ablaze.floorp/.floorp/profiles.ini
/home/jrd10/.var/app/org.qgis.qgis/data/QGIS/QGIS3/profiles/profiles.ini
/home/jrd10/.var/app/com.github.vkohaupt.vokoscreenNG/config/vokoscreenNG/profiles.ini
jrd10@jrd10-G3-3500:~$ ^C
Thank you for your comments.
[updade]
After this message from online command
cannot locate base snap core22: No such file or directory
I see...
jrd10@jrd10-G3-3500:~$ sudo snap list
[sudo] password for jrd10:
Name Version Rev Tracking Publisher Notes
bare 1.0 5 latest/stable canonical✓ base
core18 20250701 2934 latest/stable canonical✓ base
core20 20250526 2599 latest/stable canonical✓ base
core22 20250612 2045 latest/stable canonical✓ base
core24 20250618 1055 latest/stable canonical✓ base
drawio 28.0.6 252 latest/stable jgraph✓ -
gnome-3-28-1804 3.28.0-19-g98f9e67.98f9e67 198 latest/stable canonical✓ -
gnome-42-2204 0+git.38ea591 202 latest/stable canonical✓ -
gnome-46-2404 0+git.4ca00c0-sdk0+git.81ba3cf 117 latest/stable canonical✓ -
gtk-common-themes 0.1-81-g442e511 1535 latest/stable canonical✓ -
joplin-desktop v3.3.13 109 latest/stable james-carroll✪ -
kf5-5-110-qt-5-15-11-core22 5.110 3 latest/stable kde✓ -
mesa-2404 24.2.8-snap183 887 latest/stable canonical✓ -
snapd 2.70 24792 latest/stable canonical✓ snapd
spectacle 23.08.4 179 latest/stable kde✓ -
thunderbird 128.12.0esr-1 751 latest/stable canonical✓ -
jrd10@jrd10-G3-3500:~$
jrd10@jrd10-G3-3500:~$ sudo snap remove core22
jrd10@jrd10-G3-3500:~$ sudo snap install core22
And now... this error message!!!
jrd10@jrd10-G3-3500:~$ thunderbird
Content snap command-chain for /snap/thunderbird/751/gnome-platform/
command-chain/desktop-launch not found: ensure slot is connected
jrd10@jrd10-G3-3500:~$
[an updated update]
jrd10@jrd10-G3-3500:~$ sudo snap refresh
thunderbird 128.13.0esr-3 from Canonical✓ refreshed
jrd10@jrd10-G3-3500:~$
Now, everything is ok
José