Mobile App Payment Gateway Integration

I need a payment gateway integrated into my mobile app.

Essential Requirements:
- Integrate either Stripe, PayPal, or Square.
- Ensure secure transactions and data protection.
- User-friendly interface for seamless payment experience.

Ideal Skills and Experience:
- Proven experience with payment gateway integrations.
- Strong mobile app development skills.
- Knowledge in security protocols and data encryption.
- Familiarity with UI/UX design for payment interfaces.

Looking for a developer who can deliver a secure and efficient solution. Please provide examples of previous work.