Greetings. Please note : Acne is a common problem in teenagers and young adults. Excessive consumption of milk and milk products can worsen acne. Reduce intake of chocolates and junk food too. Use a topical retinoid cream daily night. You may need a short course of antibiotics. Forehead pimples even respond to use of a good antidandruff medicated shampoo. Discuss other suitable forms of treatment with your dermatologist. Pimples may often leave spots especially of not treated or if we burst pimples or pick them. You'll need skin lightening creams for a specified duration to reduce the marks , and this could also be dealt with chemical peeling. Also you must use a sunscreen to prevent darkening of the spots. For scars, creams may not work n you may need procedures like microneedling, microneedling rf, fractional lasers, prp or subscision or a combination of these. Send in your pictures if you need further assistance on private consult. Or see a dermatologist near you and discuss the same with him. Hope this helps. Warm regards