Dark spots and black patches. Photo!

Hello, I got hell lot of small small pimples kind of stuff on my two cheeks. I believe it is because of some product reaction. I consulted doctor and he prescribed adapelene( acneved duo) and clear gel. After applying acneved duo heat bumps got supressed but it left very big dark spots on my face. I was sufferng with vitamin d deficiency for which doctor suggested to take sunlight morning time for half an hour. I took sunlight between 8 am - 9 am but still i got black patches around my mouth( not sure if it is because of sunlight or ointments he suggested). Its been two months , he suggested pluerur serum and suncreen. But i found only 5% change. My face( both cheeks and forehead) is filled with black dark spots and also dark patches around mouth. Can you suggest me if there is any treatment that can cure my problem in 1 month and in low cost. Does chemical peels solve my issue or can you suggest any ointment that solves dark patches around my mouth on priority. I have attached photo