Dear Haseeb bhai Jazakallah for your mesg. Detrgent wash and inferior quality cheap polishes and waxes dull and fade the paint as such low quality waxes dont have good quality uv protection and sun blockers, may i know car age ? and its skin color ? so can propose u right products
about repainted pannels, need to wet sand , compound, polish and than wax coat , inshallah it regain its lost smoothness, shine and reflections. if u dont have experience than ask ur paint shop do all this for u , in my view 3m 2000 k grit paper wet sanding than meguiars m105 compound with rotary and m205 polish will do the job inshallah