I want to program two different cross-platform apps in Xamarin (C #). If person A is added to a list in app A, person B in app B should see this list (with person A added). There should also be a chat between the people, etc.
What would you recommend to save this data? What kind of backend would you use? Are there any simple sample projects on GitHub that I can understand and learn better? If you need more info please ask.