Test your backup
Copy important files to a separate device and open a file from it. Keep a second copy if possible. Test recovery by restoring to a new folder and verifying the file. Disconnect the backup before changing partitions.
Collect diagnostics
Record the time and the step that caused the issue. These commands show the release, storage use, and recent warnings for the current boot. Before sharing logs, redact usernames, private paths, addresses, and keys.
cat /etc/os-releasedf -hjournalctl -b -p warning -n 50