nextcloud/server ? reverse-engineered prompt

Build me a self-hosted cloud server, like a private version of Google Drive or Dropbox. I need a safe place to store and sync all my files, contacts, and calendars so I can access them from my laptop and phone. It should have a clean web interface where I can manage everything and easily share files or folders with other people using a secure link.

A key feature is that it should be expandable with apps. I want to be able to add other tools right into it, like a dedicated calendar app, a contact manager, or maybe even a video chat service. Let's use the open-source Nextcloud server as the foundation for this. Security is really important, so please build it with strong encryption and support for two-factor authentication. You can look up the official documentation for the setup if needed.