Building an API is dificult. When you have a database and you want to expose the data you have to the world or to yourself, it can be challenging and requires a lot of experience working with it. You need to know best practices, SOA, LINQ, Entity Framework and, of course, .NET. In the case you have the data and only needs the API I can make the backend that access this data in a secure and optimal way. In the case you need to create the data schema for a solution, I can do it. We can talk, we can discuss to agree what's the best option for the data to be stored and in that case I can develop anything you have in mind. Just think about your idea, think how you'd like to access your data, what level of security you want to have and we can start working together.