braintree payments installation code review (you might be awarded payment integration as a follow-up project)

We have commissioned the integration of braintreepayments API to a local freelancer and are not sure he actually integrated it properly (fully). This is a simple task where you are required to double check our code and tell us if it is properly integrated. If not, you are kindly requested to provide us with a list of what is missing / not working properly and your cost to fully integrate it. We are using PHP + JS