Mac app with built-in Fastspring payment module

Hello, I am both a client and a developer for this development service. I'm not great, but I know how to deal with xcode and obj-c a bit I would like to make and sell my Mac App outside of the Mac App Store. To do so, payment gateway and license processing within the Mac app is essential. However, I don't have any technical knowledge to support Apple Swift or payment systems and licenses. So, I request the development like this. $ Project outline Develop project template source code for xcode-based app development that allows payment through fastspring payment gateway, license registration, inquiry, and mac app update This is NOT iOS but MacOS app $ Essential Technology - Programming Language: Apple Swift, Obj-c, XCODE - Required Experience: Payment Gateway(FASTSPRING), license management, fastspring webhook API - Library: Sparkle, cocoaFob $ Essential REQUIREMENTS - Fastspring payment support - cocoaFob DSA license support - App update support using Sparkle - Must include this obj-c based main source
(*[login to view URL]) $ Development period and cost - Development Period: 5-6 business days (Negotiable) - Inspection Period: 3-4 business days - Development Cost: $ 300 USD For other details, please refer to the attached document.