Hi! I have installed Lynx Shunt - Lynx Distributor - Cerbo GX and added MultiPlus, Smart Shunt and a NMEA2000 adaptor. The Lynx Shunt included two terminators and it's manual stated that one should be inserted into the unused port. Where should the other be inserted? Into the Cerbo GX? According to the reseller no one should be used since I have N2K connected, which already has terminators. Is this correct? To me, I find it strange since it is a different network.
VE.Can and any CANbus extensions are terminated at both ends of the entire length of the bus. So where the terminations go depends on how things are connected.
In a simple system with just the Cerbo and Lynx Shunt, one termination plugs into each device with the RJ-45 cable connecting the two devices.
If you extend the but with a CANbus adapter then multiple taps to various devices, then one termination will PROBABLY plug into Cerbo with the other termination supplied on the end of the CANbus trunk. This would assume you looped from Cerobo to Lynx Shunt to CANbus.
I have connected according to the picture. If I connect the VE. Can > NMEA2000 adaptor to Cerbo GX I have no room for any terminator on the Cerbo. 
You should use a separate tap for Cerbo and the Lynx Shunt off the N2K bus. Keep the VE.Can cables less than the CANbus spec for max tap length.
Otherwise, rewire so VE.Can goes to one end of the N2K bus in place of that end's terminator then terminate at the Lynx Shunt.
The second part I understand and make sense, unfortunately it is very difficult and takes a lot of time to do (one end of the N2K is up on the flybridge and the other at the lower helm and the Cerbo is low in the stern, in the middle of the N2K backbone) so... the first part sounds more interesting. What do you men with a separate tap? Is it a special T of some sort?
You may get away with it the way you have drawn it but the length of ethernet cable to reach both Cerbo and Lynx Shunt may exceed the specs for stub length.
The VE.Can from Lynx to Cerbo is 3-6 meters (not sure) and the VE.Can > N2K is 1+2 meters.
Do you mean double VE.Can > N2K cables like this (see picture)? 
You do not need the connection between Lynx and Cerbo, that is on the N2K backbone. Also make sure you remove the fuse in the VE.Can to N2K network as you do not want the Lynx and Cerbo providing power to the N2K backbone.
In this approach you do not need terminators on the Lynx or Cerbo as the devices are spurs. A CAN network requires only 2 terminators, at each end of the network.
