Paypal premade Express buttons in unity?

Hi gang is their a way to add your paypal buttons in unity and a callback to unity for
players to purchase items?

(the buttons payola gives u the code for after u make one

(Im not interested in buying your packages i want to learn how to code it myself so i know how it works for my game) *no offence

Does this help you?
https://developer.paypal.com/docs/integration/mobile/verify-mobile-payment/