My skin is oily and i get pimple fast and when the pimple goes the mark takes a long time to go, what should i do?

The cause of your new acne may be hormonal. In puberty, skyrocketing progesterone/estrogen fluctuations lead to increased sebum production/clogged pores. Products with benzoyl peroxide, to penetrate clogged pores/extract impurities, is a safe option. But for women experiencing painful, cystic acne , visiting a dermatologist is your best option. Oral contraceptives may also help.