My dermatologist suggested to use adapalene in the night and phosphate gel in the morning but i got pimple anyways. what am i doing wrong?

Nothing except ...: Medicine is not magic. Adapaline is a combination of two meds which make the surface cells of the skin where you put it peel off. There are different strengths and vehicles in which it is formulated. Frequently after 6 to 8 weeks of use 80% of people report good to excellent results with those meds. After giving it an appropriate time trial speak to your doc if not satisfied.