oh my.... oups, i was mapping the wrong property for user language :s
==> it must be: userProfileLookup(Current User (Login ID), "SPS-MUILanguages")
thx a lot! it answer a part of my request 🙂 🙂 🙂
Yes, as i said, it's partially answer a part of it 🙂 Now i can made my form multilingual more easiest.
But, I also need to be able to manipulate SPcontext into a nintex form like we do in others solutions