There could be number of disorders which manifest as Dark black marks or hyperpigmentation
on face and the treatmnet definitely depends on the underlying cause. So the treatment can only be prescribed after analysing your face. However in general for facial pigmentation, the preventive measures that you should follow are-
1) Avoid sun sxposure, use a sunscreen of Spf more than 30 even if staying indoors
2) take a vitamin c supplement
and antioxidant supplement on daily basis
3) dont use fragrant creams or cosmetics over your face
Avoid applying creams without doctor's prescription, melacare
as such is a good cream however long term use and sudden withdrawal can lead to rebound hyperpigmentation, thin dry irritated skin etc. Take care.