Can we make any type of complex app app using react native?
or
Native Android app (Java) will be useful for complex app.

I need your suggestions.

Go for native

Well if it’s React Native vs Java/Kotlin, go for native (as in Java or Kotlin). Unless you’ll want to do an iOS version later on as well, then you’ll have to think if the effort to do it all again in Swift is worth it or if it’d be a better idea to go cross-platform from the get go. Even in that case, I do not recommend React Native. I’ve heard good things about Dart for that application, so maybe you could dig into that if you are looking for cross-platform on the long run? But if you are only gunning for one platform, always go native.

Depends on functionality though, if it uses lot of native features, then native is better even if it's possible in React native.

You can, but should you?