How do i make part of an object disappear both in rendering and collision with triggers?

making a puzzle game where you can create a small tear to another world but every time i try it the whole object appears or disappears. I need some serious help with this ,the the game is supposed to make a circular area where only part of the object disappears/reappears when it is activated but it always destroys/creates the whole object

Removing only a section of an object is quite complicated…I would suggest you just delete the whole object and instantiate a different, “teared” object in the same spot.