Unable to switch from high beams to low beams and high beam flickering on and off?

When I first got this truck it had a light bar attached to the bumper that I used as brights since the low beams worked and the dimmer switch did not work. Then recently I hit a deer and it knocked the light bar off and tore the wires, so I would only use the low beams as normal and just didn't use brights/high beams. After a week the high beams flicked on and I was unable to turn them off, let alone I had no idea how they even turn on in the first place. After a few days of just using the high beams and avoiding highways my headlights began to flick on and off. I've been looking for replacement dimmer switches/wiring for my truck but haven't been able to find specific replacements that would fit for sure. Any recommendations on what I should do and specific parts I should buy to fix this problem?