Can't get my brake lights to work

I have a 1990 chevy z71 pickup The brake lights worked when I got it but they would stick and stay on until i kick or move the pedal.soon they quit working completely all my other lights work except my back up lights. I’ve replaced the brake light switch and when i ajust it the way it says they still don’t work but I can move the switch and they will work but won’t turn off when I move it back they turn off but won’t come on again when i hit the brake. Help I ‘m lost