Is it safe to increase the speed of graphics card fan ?

Yes its perfectly safe, its actually advisable in your case.

whats new in my case ??
how much should i increase the fan speed ? should i keep the fan speed the same at all times ?

eh? I never said anything was new... Just that its advisable to increase the fan speed if your GPU temps aren't satisfactory.

I'd personally create a fan curve in MSI Afterburner, so that the fan speed increases as the temp increases, so that when your not gaming your graphics card is nice and quiet.

I would ask WHY it is overheating. The card should not overheat under normal use.

Is airflow bad in your computer case?

Are you overclocking the card, resulting in increased temps?

The high temps are a symptom of something. Increasign the fan speed will take care of the symptom. It is not fixing the actual problem.

IS gaming, normal use ?

how do i get the best fan curve for me ?