Light problems

I'm having issues with some of my lights and I'm not sure where to start looking to fix them. When I turn my side lights on, I'm getting front and rear lights as normal but when I turn the full lights on, I'm getting front lights but no my rear lights. Also, my front passenger and side passenger indicator lights aren't working. I've checked the bulb on the front and the bulb is fine.

If anyone could help, that would be great. Thanks

To start with check the earths, look for any brown wires at the rear and clean up the contact points where they screw into the chassis

I've had a look in the boot and there is and earth wire on the drivers side which isn't connected to anything. Also there is a wire that seems to come from the front of the car which is connected to nothing. Should these be connected?

yeah i would say so, trace them to where they go and clean up then reattach to chassis. the one from front of car i would say is fuel level sender/pump

The brown wire is connected to the chassis but goes nowhere. It's a really thick wire, could this be an old sub earth? It doesn't look like the other earths. I'll take a picture.