Need help with ASP.NET Core 3.1 API for use with Android

Hi all, I hope everyone is well, healthy and indoors!

 

Pardon my lack of correct terminology, i'm looking for some assistance or a tutorial that will help me do the following:

 

Build a restful API using Visual Studio 2019 that I want to publish on my local IIS which also houses MS SQL Server 2016 which will take into account:

 

I want to build an Android App that can send data from textboxes through the API to a SQL Server Database and also use values from a table or two as values for dropdown boxes?

 

I have searched... (Promise!) but because i'm not entirely sure i'm asking for the right thing, my search is hitting dead ends or ancient tutorials that don't apply any more...

 

Any and all help is much appreciated.