Dark spots of pimples take little time to disappear as they extend into deep layers if skin even if seen as spots on the surface. Visit a qualified dermatologist for prescription based creams and chemical peels according to your skin type to reduce pigmentation. Keep patience, be regular and follow your dermatologist advise strictly, your problem will be solved. Do not buy OTC or advertised fairness creams as they contain steroid and it may worsen your provlems. Hope this helps.
Dr Vijay Adhe
Eternis Skin & Hair Clinic