I managed to fix the problem by completely destroying the "263" folder in order to force Opera to recreate a new one. Of course before, I had made a copy of the original file. From this copy, I selected the “Extensions” and “Extensions Scripts” folders as well as the “Bookmarks” and “Preferences” files then I copied and pasted them into the new folder.
As for the language problem. I found in the "263" folder, a file called opera_opera.desktop. I made the changes recommended for the Opera.desktop file on this one.
I lost my passwords, my addresses as well as my favorite search engines, but I was able to solve the problem. I could have avoided destroying everything if I had known where the passwords were stored so that I only destroy this single data file.
But it works again; That is what matters.