As u mention ur 22ys old and u r suffering past 5yrs , that means it was started 17yrs old of u .
actually it is not related to food , it is under control of androgen hormones these are male sexual hormones .
normally most of the males get the ance in this age group . in acne also 3 grades are there 1,2nd 3rd grade and cystic acne
. as u mentioned dark marks on ur face mostly it is 2nd grade , this darkness is post inflammatory hyper pigmentation . it take time to clear.
solution for ur acne is internal treatment is require to control androgen hormones
for that homoeopathy has good solution.