Is it about dodging his attacks or just damage ? Because honestly I tried to fight him, took me 9 minutes to beat him (though many mistakes, and I had barely any health left).
To give you a few tips :
To dodge him, you can abuse his AI, you first bait an attack, dodge just out of range (careful as his hitbox lingers a bit), get close to him, and wait for him to prepare his attack and pass behind him when he does, then finally attack him, rince and repeat (always better to demonstrate)
For the second phase, just try to be high on stamina when you feel like his head is gonna be exposed to deal as much damage...and have a lot of patience, you deal barely any damage.
Edit : Also thanks for the tip on stamina, it really does help during this fight.