First I would start by disconnecting the damaged wires. Get a test light and connect a good ground. Now turn on vehicle running lights and Four way flasher. Touch to wires leading form front of trailer. If light stays on it is the running lights, if it flashes it is the brake/turn signal. If no light from wire it is probably the ground. To test for ground, connect test light to 12 positive source and touch wire, if it goes on that is your ground. Once you find ground you should be able to connect it to the same color wire to the rear. Now touch on of the light wires to the other wires and see what happens. if brake/signal light comes on steady, that is the running light. If it flashes then you found the right wire. Then just connect up the other wire to the running lights and verify that they work.
Hoe this helps,.
