ok before this my taillights would turn off when i press the brake, so i replaced brake light switch, and can't figure out what to do to fix this truck or where to start and what wires to test. my friend tried to help and i think he cut a bunch of wires idk because i need to go through under dash or have someone go through it to make everything work etc. but until then i need to get my taillights and taillight running lights to work! thank you

 

Without knowing what wires were cut and what else was done, It is impossible to say what needs to be done. You have get in there now and figure out what wires go where and figure out where to connect them. If your taillights went off when you pushed the brake pedal then your problem was probably at the taillights. A loose or corroded connection at the bulbs. Also could be a bad socket or bad wiring.