Nadine,
The recording number isn't incrementing because your offset (18) is incorrect when you attempt to read the current recording number from the datafile. If you change 18 to 17, you should see this part of your code start to work again.
As for the file question (Para_MahineDefaut.txt and Para_Mahine1.txt), it isn't clear what behavior you want. Do you want the user's choices always to be saved in a file called Para_Mahine1.txt every time, without any prompts? If so, you'll have to specify a full file path to your last Open/Create/Replace file node; the default name input does not tell LabVIEW where to save the file, and is really only there for interactive purposes (when the user is prompted), so you won't need that if you want the file to be saved programmatically. Your current input to file path, an empty path, is not accomplishing anything.
I don't want to make you feel bad for asking for help, but you seem to have questions about every step of your project, and you don't seem to make an effort to keep each discussion thread devoted to a single problem. This behavior, combined with the fact that it's often hard to understand your English, makes it more likely that your questions will remain unanswered.
I would suggest that you get some personal help with your LabVIEW programming skills (a class, a co-worker, etc.) to complement the help you are trying to get here.
Regards,
John