Private Shopify App

Hello, Welcome on board ! We want to create a place where people can buy and sell original art. Not a simple marketplace but a Shopify store where people can sell us their products like to a pawn shop. We must make it easy for sellers ! Functions - Front End : 1 - Image + text page --> cancel or next button. 2 - Search bar to select the product to sell - if not existing product : text + next button. 3 - Set price with fees auto calculation and display different fees. 4 - Upload different real pictures from camera + videos. 5 - Upload different real pictures from camera or PDF files. 6 - Image + text page --> cancel or finish button. Then send well organized data to a mail address or save to cloud / other available memory. Back End : Organized like client file - Product + Seller name 1 - Easy view - open - play - download data 2 - Send auto filled notifications to Seller : Buttons 2.1 - Approve button : send notification + invoice to seller e-mail address then add a tracking number form + shipping label pictures upload button to Front End. 2.2 - Negotiate button --> we enter an amount + auto fees calculation --> send notification to seller then add Accept or Decline Offer button to Front End. 2.3 - Decline Button : send notification to seller email address. 3 - Track the parcel Good ideas and Genius are welcome !