Build a website that interact with steam api

Hello, I am looking for a developer who can build a website where after the user pay, it will tell a steam account to send a trade offer depending on the amount the user purchased. And it should accept PayPal, Credit Card, and TF2 Keys. The website should let the user log in from steam, and check their inventory. If they have tf2 keys, they can select them to pay and the bot will send a trade offer to get the keys for nothing.

Example: https://steamlevels.com