Development of the main functionality of the application, i.e. why the application is being created, what problems it will solve (in this case, it is important to build on the proposals of competitors and look at the best examples in the field).
Development of the server side and API (where information is stored and most often processed) + testing.
Learning to use the server side.
Design implementation.
Team: project manager, designer, Android / iOS developer, backend and API developer, QA specialist