In my case the button was glued additionally. Cut around it to make it loose.

Use the 2mm hex screwdriver and remove the tiny screw on the side of the bell housing.

Use the pliers to unscrew the button. Screw to the left.

You can't break what is already broken. It should come off easily, so keep cool. Although, in my case, the button top broke off.

Don't forget to turn off the bike!