I solved it fully ! 💪
I have redone the wiring using the attached schema.
wire xin mo 18 pin.jpg

After that, in the menu confirmed the mapping for player 1 and player 2.

I assigned Hot Key for player 1 to L2, and R2 for player 2.

After that it worked well, except the player 1 and 2 were swapped for an unknown reason, and even in the paf conf menu it changed nothing (a bug?).

to solve it I modified the recalbox.conf from:

emulationstation.pad1=03000000c0160000e105000001010000:Xin-Mo Dual Arcade emulationstation.pad0=03000000c0160000e105000001010000:Xin-Mo Dual Arcade

to:

emulationstation.pad0=03000000c0160000e105000001010000:Xin-Mo Dual Arcade emulationstation.pad1=03000000c0160000e105000001010000:Xin-Mo Dual Arcade

that is it. hope it will help others that me.
@admin, you can mark it as solved.