Hi Monique, there’s no converter or tool that changes your hybrid app to a native one. You need to create a react native app from scratch, but native apps are always offline-first.
Offline-first is an architectural concept and the question is wether your Mendix project already uses this approach and or how much effort does it costs to implement this?
I would suggest this article on offline-first: https://docs.mendix.com/refguide8/offline-first#1-introduction