"I mean you train me all game to find the differences and avoid the monster and the last challenge is about timing and attacking and all"
Damm, this actually oversight that we didn't provide any info about what you should do against him.
Yes, you should kill him with a sword, i guess we should increase damage output. He will be dead with 12 hits.
The tactic against him is pretty easy, but i guess if only other people played Legend of Grimrock.... i mostly was inspired by it when created this combat loop. You should constantly change your position to make him rotate, hit him when he comes to you and just step left or right.