Hey,
That monster is one of the most difficult ones; It has armor on the front and a weakpoint on the back.
Something that might help is understanding the sword swings; Right mouse button will swing your sword from Right to Left. Left mouse does the opposite.
If you hear the monster panting on your left side, try to use the sword from the right; you'll have a better chance of hitting him since you wont hit his armor.
Im happy to hear you got so far! It is quite difficult. I'm pushing a small patch today with a bunch of small fixes.