E-commerce App for iOS & Android

I require an adept mobile app developer who can create an e-commerce app on both iOS and Android platforms. The primary functionality of the app should focus on e-commerce, providing seamless online shopping experiences for users. The must-have features of this e-commerce app include:

- A comprehensive product catalog: The app should enable users to easily browse through a vast array of products, offering detailed information on each including price, specs, and images.
- A user-friendly shopping cart: Users should be able to conveniently add and remove products from their cart and review their items before checkout.
- A secure payment gateway: The app should guarantee safe and secure online transactions, supporting major debit/credit cards, and popular digital payment methods.

Proficiency in Java, Swift, and e-commerce app development are highly preferred. Proven experience in integrating shopping carts and payment gateways will be greatly advantageous.