Wiring troubles

What is the issue? You will need to run a good hot and ground, then use the cars wiring to trigger added relays to actually operate the trailer lights. Not sure what the wiring protocol for your 7 pins are, but here in the US you would also need a diode bridge to make the turn signals operate the same bulbs as the brakes.
Do not try to power the additional lights directly from the vehicle, the lights are run on very light wiring and the computer will not handle the extra load without the relays you will damage the BCM.