can I put a web page created with reactivate convert it react-native ?, and if possible how, I can reuse the same server on the web page, with the rea-native app so that the same user can be accessed , the functions and privileges of the same user both on the web and in the app.
It is possible to use Django as back in react and react-native, the same server for both
Yes you can use the same backend for the two applications. Both should use the same process to login / signup.
Your two applications can bring information from https://tuapi.com/
If you want to share code between the native app and the web you can take a look at link
You can also create a monopoly to have the project in React Native, React Web and the business logic using Redux / MobX or what works best for you in the same place.