Dual Platform E-Commerce App Development

I'm seeking a skilled app developer who can expertly utilize Kotlin for Android and Swift for iOS. The essential features should include:
- User login and registration: A secure method for users to register and log in to the app.
- Push notifications: A system to send real-time push notifications to users.
- Get data from server and display response interactively.
- In-app purchases: We need a seamlessly integrated system for in-app purchases.
- REST API connection: The app has to connect to our existing API to extract and display data.

The target audience is young adults, so the UI/UX design should be appropriate and appealing to that age group. It's crucial that the app is developed for both Android and iOS platforms simultaneously. It's important to ensure equivalent functionality and experience between the two versions of the app.

Ideal candidate should have strong experience in mobile app development in both platforms, understanding of UI/UX optimized for young adults and a proven track record with in-app purchases system and API connections. proven skills of JSON, JAVA, APIs, FIGMA, JWT.

Backend is operational and developed in JAVA/SPRING FRAMEWORK. Understanding of integrating with such environment.

Understand payment gateways and its responses to implement customer payment solutions.