Integrate backend for payment methods and databases

I am looking for a skilled backend developer to integrate payment methods and databases into my website (www.oddco.ca). I am looking to integrate secure payment gateways that allow users to pay for products on my site. I also need a database system that allows users to sign up/log in, be added to mailing lists, save user high scores for leaderboards, and other basic functionality.

Payment Methods:
- PayPal
- Credit Card
- Debit

Database System:
- MongoDB/MySQL/ETC...

Requirements:
- Integration of 2 or more payment methods
- Implementation of MongoDB as the database system
-Ability to hold users scores for use on a leaderboard
-Mailing list and user sign up/login

Ideal Skills and Experience:
- Experience with integrating payment methods such as PayPal, Credit Card, and Stripe
- Proficiency in working with MongoDB for database management
- Strong understanding of backend development and API integration

Please note that I am specifically looking for a developer who has experience with integrating multiple payment methods and working with any database system you recommend.