Funfiftyplus: I am one that just can't seem to get the hang of the fight. I push the buttons when the letters show, but nothing happens. I have the difficult QTE unchecked. I have a newer mouse and computer. All drivers are up to date. Perhaps with more practice, but reloading over and over again destroys the fun of the game. I would like to know if someone would help me out by taking my save game and getting through the fight and sending the save back to me.
Did you have trouble fighting the prison guard in the Prologue, too? If you did have trouble. note that you have to be pretty quick on the trigger with the fistfighting QTEs, especially when they come in combination.
If the controls were responsive in the Prologue fistfight, but not now, try reducing your graphics settings. The big crowd in Flotsam is very hard on your frame rate, and this reduces the responsiveness of the controls, too.
Also, watch out for the combination QTEs, for example when the game flashes an "S" and then a fraction of a second later flashes a "W". If you miss the combination, Geralt frequently ends up getting body-slammed.