rear driver side turn signal and brake light

There is probably a contact problem in the socket. You need to do some testing with a test light to determine if there is power coming into the socket.

the bulb works in the socket it lights up it just don't flash or brighen when I hit my brakes.. It works as a taillight just no flashing for turn signal and no brightening for brakes.. Only rear passenger side

Sorry it's my driver side!!

There are 2 circuits in that socket and you have only verified one.

The tail light works, the light that suppose to flash and brighten when I hit my brake lights up just don't flash, and the back up light works.. There is three lights in one tail light The tail light the turn signal brake light and the back up light they all light up none flash or brighten was told could be the circuit board

It's pretty apparent that you do not understand electrical circuits at all so you will likely have to pay a shop to do this testing for you, As I already stated, the tail lights and brake lights are entirely different circuits that utilize a single 2 filament bulb.

I understand this but in my truck there is only one big plug that plugs into a circuit board thing witch has the 3 different bulbs hooked into it.. If each light has a different set of wires running to it what you are saying would make since but for my year of truck there isn't but one big plug that hooks up to a black circuit board thing that is screwed to the taillight.. I replaced the black piece that has the one plug in I have no clue what it is called and the problem was fixed

That would have been a replaceable /individual bulb socket. They fail often.