WINDOWS DESKTOP APP - C++ DEV

I need a Windows software application that will be sold and used by hundreds of people. It’s an optimization application, so the code must be highly secure—that's why I’m here. It must be developed in C++ and should also have a well-designed UI, matching the provided mockups. The application should execute optimizations instantly, with no delays. Most importantly, it needs a sign-up/sign-in system to connect to our existing customer database. This will allow us to distinguish premium users, unlocking additional features for them, while basic users will have restricted functionality. GOOD PAID