go to a dermatologist and get some advice from 'em. there are topical treatments for hair loss those are minoxidil and finasteride. but you have to keep using 'em for the rest of your life.
on the other hand, there's a permanent solution for hair loss which is expensive, and that is hair transplantation. it is done through a micro surgery and they'll be taking a linear strips of hairs from the back or sides of your head and those hairs are then transferred to thinning or balding areas of your head.