My buick 1996 park avenue lights has no parking lights, side lights and back lights at all. brake lights work

My buick 1996 park avenue lights were dimming by themselves idling with
car I took to mechanic he could not find problem then had headlights on
when you start the car because headlights did not work at all eventually.
Then next day interior dashboard lights strobing I took back and I have no
parking lights and back lights at all. So I have been driving in day only.
Does anybody have a solution I have checked all fuses, One was out the
turn signals I got working again. I even replaced a relay fuse a 20A