Magento Grocery Marketplace with Price Comparing Features

70% Payment will be made after completion of 50% work completion. No upfront will be given. Source code will be my property. I need an Magento multivendor Web app for eCommerce with features of price compare from others and demand a new price from company by buyers. Reference app, I'll show you and you can take idea from there. It will be a multiseller application, where sellers can create their account and post their products to sell. And they can change their product price at anytime on buyer demand. Seller should be having the feature to approve the customer price or reject or modify or give a new price. There should be star rating and review feature below every product alongwith Buy Now and add to cart buttons. There should be 2 prices, 1 MRP and one our price alongwith discount percentage. There will be Admin Panel (Should be having all the features to monitor any account or edit or modify any account, total sales in last some days or months or years, total discounts given etc. Seller Panel (Return or refund price, Chat with customers) Buyer Panel (Share any products on social media and mails also or other apps also, demand new price from sellers, rating and reviews) Logo should be beautiful. Database should be faster. Web App should be lightest and fastest.