GST Billing & Accounting WebApp Development

I'm looking for an experienced developer to create a GST Billing and Accounting web application. This app should support multiple users and be compatible on both desktop and mobile platforms.

Key Features:
- User Authentication: Two-Factor Authentication
- Functionality for:
- Sale
- Purchase
- Sale Return
- Purchase Return
- Reports:
- Sale Report
- GSTR-1 Report

Ideal Skills and Experience:
- Expertise in web app development
- Experience with multi-user authentication systems
- Familiarity with accounting and GST requirements
- Strong UI/UX design for both desktop and mobile

Please provide relevant experience and a portfolio.