I help you learn Facebook’s React Native, the second-most popular cross-platform framework for building native iOS & Android applications from one codebase.
Use Google’s Flutter.
The React Native website is a good starting point. React Native uses JavaScript to create mobile applications.
TypeScript mixes “some Java into JavaScript”, such as types. Hence the name! You have to use TypeScript if you use Angular. And you can use it with React.
You can take a peek in the “TypeScript for Java/C# Programmers” article. If you like it, then the TypeScript handbook is your friend, also in Epub and PDF.