I've released a new application called WalkWithArt.
WalkWithArt is an application that you can appreciate art on iOS and Android.
This app is implemented by ReactNative. Please check it out :)
I have some experiences to implement native apps by Swift and Java. (You can find them on my github.) However, if the app is not so complicated or you're only one developer in your startup company but need to implement for both platforms, ReactNative could be a great choice for you.
You may need to change some settings on Xcode and on Android Studio, but it's easy. And you don't need any knowledge of Swift and Java. (Of course, it's better if you know it, though.)