i need help with the backend for my flutter app

I am looking for a backend developer to assist me with my Flutter app. I have a few specific requirements for the backend functionality and the integration of third-party APIs.

Backend Framework:
- I am open to using Node.js, Django, or Ruby on Rails for the backend framework.

Functionality:
- User Authentication: I need the backend to handle user authentication for my app.
- Database Integration: The backend should be able to seamlessly integrate with a database for storing and retrieving data.
- Third-party API Integration: I require the backend to integrate with various third-party APIs to enhance the app's functionality.

Specific APIs:
- If you have specific APIs in mind that you can integrate into the backend, please let me know. Otherwise, I am open to your guidance in selecting the appropriate APIs for my app.

Skills and Experience:
- Strong experience with the chosen backend framework (Node.js, Django, or Ruby on Rails)
- Proficiency in user authentication implementation
- Knowledge of database integration
- Familiarity with integrating third-party APIs into backend systems