Hey,
Greetings from Akshay Mishra. I can help you with database, API and backend setup. I'm not very good at Unity. But I'm familiar with hybrid mobile application development and Restful API.
I can develop your backend API system in C#, .net core/web API and It can be configured in Unity. That will easy for you to configure again in the future.
Cost will be decided upon project description.
Demo app url: [!]
Backend API is written in C#, .net core
API screenshot : [!]
Thanks,
Akshay