Mobile App Server Requirements

Thanks for taking the time to attempt to help me. So I’m developing an app that needs to let some sign in to send data to a server and the rest can pull data from the server without having an account. The data on the server will be mostly text and one image, maybe two per data entry (entries only made by registered user). So I need a server to store this information, send this information to users on request, and update the stored information by signed in users. Having nice sign in option would be nice but not required since this app will be fairly unique.

Can anyone help me understand what I need for this task?

Is there any company you would recommend I subscribe with?

Gamesparks