Hi @hec2rin,
I would like to help you more, but multitouch is a very specific process that must be crafted according to your app. Corona provides you with the ability to get a unique “touch ID” for each touch on the screen, along with the ability to set the “focus” of each touch on a particular object. From there, you need to figure out how to handle it in your project, and what should happen on each phase of each touch, along with what happens when a touch loses focus on the object it started on. We (staff) can’t really know what your project is supposed to do and how it’s supposed to behave with multitouch.
I can suggest that you look here for details on setting touch focus:
https://docs.coronalabs.com/api/type/StageObject/setFocus.html
Best regards,
Brent