[solved] Columns modified after installing last jabref version

Hello,
The columns I was used to see when opening my bases changed from 2.10 to the present 3.8.2, here are the pictures:


the ‘timestamp’ date is missing, replaced by ranking, that I don’t want. I use it for sorting my entries.
I was able to add a column (in “Options” “Preferences” “Entry table columns”) called timestamp, as before, but it is now empty.
Did I destroy the information in my whole database?
I have a copy, but how can I build the setting I need?
Thanks
SoGe

My original file lost indeed all timestamp informations (I don’t know why), hence the column, added as described, in the right way, was empty.
The .bak file was not corrupted.
I have the columns I need now, with the complete file.