(Concern) Hairline treatment

As I get older, it seems that the hair volume on the upper part of my forehead is decreasing. It looks sparse, and I feel sad every time I look in the mirror. I want to have a procedure that makes the hair look full along the hairline so that there are no empty spots, but how much pain can I expect?

And I am actually worried about how long the effects will last after receiving it. If the duration isn't long, it could be a waste of time and money.