I found the problem by my self.
In VPN > DHCP over VPN -> Central Gateway -> DHCP Relay
I checked the use internal DHCP server box
I missunderstood this "internal DHCP Checkbox" I tought "internal" is LAN internal.
But "internal" is SonicWAll internal.
If the DHCP is not the SonicWall itself this checkbox have to be unchecked.
BR
Opusretis