Delivery App ERP Integration

I’m days away from launching my Instamart-style delivery app in India Locally to Andhra Pradesh built with Flutter (mobile) and PHP (backend). The core platform is ready; however, I now need a compact ERP layer added before we hit the stores... (Budget: $250 - $750 USD, Jobs: CRM, ERP, Flutter, Git, Mobile App Development, MySQL, PHP, RESTful API, Software Architecture, Web Development)