If you have no one else to help you and need to try doing something yourself, you can check a couple of things first for clues. See if either the red-marked wires (positive), or the black-marked wires (negative) are longer or shorter than each other, and reach their respective terminals without having to stretch them. Also, are any two wrapped together with tape further back in the bundle. If no help there, then this is how I would proceed to determine the correct connections.
You can identify which wire is the hot wire coming from the TV if you have a voltage tester or multimeter tester. Spread out the ends of the four wires so they don't touch each other or anything else. Then, back your TV up to the trailer and connect the 7-wire plug. Then touch the black lead from the meter to a good ground on the camper frame, and the red lead to each of the four wires, one at a time. The one that is hot is the one charging the battery from the TV. I suspect it will be one of the wires with a red mark, but you want to know for sure.
Then touch the red test lead to that positive wire and the black lead to each of the remaining 3 wires one at a time. When there is a reading or the light
comes on, that is the negative wire grounded to the frame. I suspect it will be either of the wires that have a black marking.
If for any reason either the black or the white wire shows as hot when connected to the TV, then stop, since the PO messed with the wires and his markings are meaningless. Do nothing until a qualified person can help you.
That leaves you with two wires remaining unidentified, one a positive and one a negative. They provide the power and ground for the connections in the camper. Since the yellow wire has red markings also, and has the 30 amp fuse that would normally protect against excessive current draw from the trailer, my best guess is that wire is the other positive wire. Connect just that wire to the positive battery terminal. Then connect just the remaining ground wire to the negative battery terminal. You can then check to see that you have power in the camper. The lights
should come on and any motors should operate normally.
If everything operates fine, you can then disconnect the ground wire, add the TV hot wire to the positive terminal, and then add the two ground wires to the negative terminal. Always connect the positive wires to the battery first, then the ground wires.
You are back in business.