To build our app, we used Flutter. It is an open-source framework from Google that allows you to build platform independent apps, based on the programming language Dart.
To manage our codebase, we used Gitlab. We had a repository for both the frontend and the backend. We also created a Kanban board to have an overview of our open tickets and who was working on which ticket.
In order to clarify quick questions outside of our meetings or to keep each other up to date, we set up a Discord server where our communication took place.