Hello Pascal
For the translations of the texts in the program I use a simple txt file for each language.
You can have a look into the IconEdit program, there you can see how I handled the multilanguage.
Icon Editor
In this program, the help files are html files written in Word.
In the 'Wine cellar' program
Wine cellar manager
I have begun to write *.cmh help files.
I saw that you use HelpNDoc for the help files, there is another interesting one, vaHelpMaker.
http://www.vizacc.com/
It was suggested by agraham in this forum.
You can post the txt file for french program texts.
Best regards