Firebase Web App Backend Fix

I'm developing a web app on Firebase Studio using Next.js, Node.js, and Firebase. I need help with:

1. Signup Backend Fix: After signup, placeholder data should be stored in Firestore.
2. Profile Modification: Ensure full name, email, and avatar are modifiable using router.js.
3. Backup Feature: Set up complete database backup.

Ideal Skills:
- Strong experience with Next.js, Node.js, and Firebase.
- Proficient in Firestore and router.js.
- Backup implementation experience.

Thank you!