Every time, i do the fist fight with him his health bar doesn't go down
even Gearalt said "how long you're gonna keep me like this"....lol

https://youtu.be/d6Pw2vMUWVk

You are aware of the fact that you actually can take the arsonist to the smithy?
He (the smithy) will call the guards, the arsonist will be hanged, and Geralt/you will get better prices if you purchase stuff from the smithy afterwards!