Turning off NAT = troubles ?

Well since no one answers me for days in old topics, I have to make new ones and also because im desperate to fix it.
Is it safe to disable the NAT funcionality on my router? ( Router model : SMCWBR14S-N2 )
Because it goes in conflict with my modem, probably because it has a NAT funcionality included on it too, im not sure ( Modem model : ARRIS TM502G )

And are there any secondary issues if I turn off my NAT?

Thanks!

Seems to me that you would only need or want one NAT working at a time. Yes I'd say it's safe if you have another one working on the modem.

Im not sure if I have one running on the modem. Are there any ways to see if that's true?
Another thing : would it affect another connections like wireless? Because im not the only one who uses internet at my home. And both of them are wireless.

Thanks!