React Native
you can check out for developing native cross-platform mobile apps, then they React Native. It uses React and JavaScript for producing high quality native mobile apps.It's the right choice for all web developers who wants to become a mobile app developer and already familiar with technologies like JavaScript and React. If you are one of them, then I suggest you learn React Native in 2020.
Also, there are a lot of resources to learn React Native, both free and paid.