Hi,
No need to be sorry for being French

I'm too
How do you try to connect to the NASLite from the web ? Do you have a modem router box (Free, Neuf etc).
In general, the "gateway" is the internal IP address of your modem router, something like 192.168.?.? You set this in NL. Then you select a port not used by something else and direct it to the IP address of your NL box (this is to be done in your modem router / ??box). Then from the internet, you type the unique IP address of your installation (you can see this by going to
http://www.whatismyip.com) followed by

? (?? being the port address).
I hope this clears up things a bit for you and that I haven't made an error (haven't used this access for a very long time).
Salutations