[solved] Columns modified after installing last jabref version

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?

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.