Rebuild a Shopify ecommerce site using Gatsby + React

Hi, I have a shopify website (ecommerce site with 40 products and a few other features). I'd like to re-build the front-end using Gatsby and react (Server side rendering with Javascript Frameworks / Single Page Application) Please bid with your experience and other sites you have built using this framework, and all the info you can send. Also an approximate budget would be great. We need two budget options: OPTION 1. KEEP SHOPIFY BACKOFFICE AND REBUILD THE FRONTEND USING GATSBY+REACT 1. Gatsby + Shopify Ecommerce Site: - We will be using JavaScript SPA/SSR (Single Page Application /Server Side Rendering technologies). - A server that supports this runtime tech will be needed. The chosen bidder should make suggestions - It must be considered that the development involves only the connection of the Backend API WS with the Shopify Backoffice. - Backoffice features that Shopify does not support can't, therefore, be included as part of the development. - The database will be Shopify. - The development is at a frontend level with API integrations.  - A scope of work document must be created and sent to us. - The site will be responsive for PC, tablets and phones. - If widget integrations or external components are required we will let you know before starting so the bidder can include them on this quote, right now we are only considering Google Analytics and the current Chat.  - With the current budget, only one payment gateway is considered. - We will provide all the designs before starting, if the Figma file is incomplete, that page won't be created.  -  3rd party licences are not considered within this budget. ================================================================================ OPTION 2. REBUILD THE ENTIRE SITE FRONTEND AND BACKEND, USING GATSBY+REACT 2. Gatsby Ecommerce Development > FrontEnd > BackEnd > BackOffice - We will be using Javascript SPA/SSR.- It is considered as development technology API PHP Framework CodeIgniter- MySQL Database - A server that supports this runtime tech will be needed. The bidder must make suggestions.  - A scope of work document must be created and sent to us. - The site will be responsive for PC, tablets and phones. - Backend won't be responsive (desktop version only) - If widget integrations or external components are required we will tell the bidder so they can include them on this quote, right now we are only considering Google Analytics and the current Chat.  - With the current budget, only one payment gateway is considered. - We will provide all the designs before starting, if the Figma file is incomplete, that page won't be created.  -  3rd party licences are not considered within this budget. Best, C.