Hey ! i've found my problem ! you have to modify another file too
here is my workflow :
1] i connected the Rpi 0 W on my router using SSID + KEY of my wifi network
2] i went into the settings menu to sse my IP and NETBIOS Name : it was "RECALBOX"
3] using windows and CMD command prompt, i typed "ping RECALBOX" to get the IP , as the IP was set in IPV6 ... so i was not able to retrive the IP then the ping command send me the IP in IPV4 format
4] I connected to the PI 0 using KiTTY ( or PuTTY, its the same) using the ssh connection mode (port #22) and the previous IP address
5] when prompted to log in ( "login as ") i typed "root", and the password "recallboxroot", then i saw a "#" on the begining of the line
6] Once Connected : i typed this command to re-mount the boot partition in RW, so i'm able to save the file " mount -o remount, rw /boot" then hit enter
7] I typed "nano /boot/config.txt" to open the nano text editor to check my config file . it was all ok (press crtl+X to exit )
8] I typed "nano /recalbox/share/system/recalbox.conf" to edit the file . near the "H" section, I changed the global.videomode=HDMI_xxxxx to "global.videomode=default" to allow all games to run on Composite screen . then CTRL+O to save the file then CTRL+X to exit nano .
9] i typed "reboot" to restart the Pi0 then i was able to run games on my composite screen
now my problem is solved, then i shared my solution
Have a Nice day folks !