hello guys. how to call the boss? and where i can find crub-humans?

You have to go up to the pile where the skulls are and there should be a prompt to lay down the item.

Then he'll come out if you bought the hunting book from Jimbo and Ned.

you make friends with the 'crub-humans' after u get the nagasaki fart in canada

The pile of debris, with the plank and the skulls, is where you're supposed to place an item. When you do that, the boss appears and will do battle with you.

You have to go up to the pile where the skulls are and there should be a prompt to lay down the item.

Then he'll come out if you bought the hunting book from Jimbo and Ned.

What he said.  You have to have started the quest with Ned and gotten the hunting manual first.  Also the Crab People are further in the sewers once you go through the emergency exit.  That said to get to the crab people you have to have unlocked Nagasaki first which you get near the end of the Canada questline.