I prefer using Swift for iOS projects, but because it sounds to me like you aren't quite sure what you want to do I am recommending Ionic. Ionic is a mature framework that allows you to release mobile applications that have a professional look and feel in a relatively short amount of time. You can always backtrack and create a native Swift application.
I recommend TypeScript. When used correctly, TypeScript can enable your application to be scalable, easy to refactor, safe, and stable. One of the biggest draws of working with any typed language is that it forces you to think about your functions' inputs and outputs. This is invaluable as it can lead to more declarative, functional style code that ultimately can be easier to reason about.
TypeScript is however not a silver bullet. Just like anything new it takes time to fully understand the concepts of types, interfaces, abstract classes, and enums. In my experience engineers who excel when using TypeScript are those who have experience working with a statically typed language.
