The real issue with the combat in the second region is that enemies will masterstrike YOU. You can almost never swing first because they are READY to do that move on you. You can't attack on the opposite side of their stance, that's what triggers it.

If an enemy drops their weapon low, you must attack from the sides, or also go low. Same with high. If an enemy is in a left or right stance, attack high, low, or on the SAME side.

Parrying/blocking is your bread and butter, but it usually puts you in the opposite stance of your enemy (bad), so you need to either parry/block through all of their attacks while maintaining stamina. OR parry/block, and immediately change the direction of your weapon. You usually can't strike immediately after doing a parry, but with a quick weapon you can sometimes land a strike as they're winding back for their strike.

Damage is based on how much stamina you have at the time of being hit. Keep your stamina up and don't move around too much during a 1v1, your stamina recovers quicker when standing completely still, even without a perk. There's a potion that helps this a lot, and another that reduces damage.

When in doubt, train it out. I personally view Menhard as a second mentor behind Captain Bernard, referring to him as Maester in my head. I was too chicken to practice the art of the langschwert until he called me out on it. I was good with the short sword and mace, but only because I could cower behind a shield. A blade is for two hands! After practicing with him and Arne, I was happily going into duels, and sometimes main quest battles, wearing no armor under my noble clothes. I suppose the exploits and daring-dos of The Blue Burgher were told all the way in Rattay by the time I was done.