Using a single database for a cross-platform mobile application and website. How to implement?

Question

Database

I work as an enikey worker in a small company. There was a need to create a cross-platform mobile application and a "bulletin board" site.
Since I did not work much in c#, I decided to make an application using xamarin. The hardest part for me (because I have never worked with it, but I have time to learn) is creating and managing a shared database. Please advise how to implement all this in general terms and throw in information on this topic. Thank you!

Answer 1

I don't understand exactly what help is needed.
Usually for such projects I raise a PostrgeSQL database with a REST interface to it PostgREST . It is raised in the simplest case with one command in the docker container . The site, mobile application and all sorts of integration modules are not set on the database directly, but on this REST interface.
This is in short. If you need details, I am ready to answer specific questions.