Build and design a Marketplace App

I am looking to build an app, the purpose of the app would be for users to be able to buy and sell luxury and limited products such as clothes, shoes, bags, watches... The app functionalities will be very similar to 2 apps that already exist. You can find these apps on App Store. Name of these apps are GOAT and StockX. This app will need to be built on iOS, Android and eventually a website later. We will need to have a back-end part that will allow us to manage orders, products, and users accounts. If you are going to submit a proposal to assist me with this project please take some time to analyze the 2 apps : GOAT and StockX and understand what it will take to get this done, it is not your typical shopping experience so take some time to analyze the different features please and if you have any questions do not hesitate to contact me. If you aren't able to provide a portfolio with minimalist, modern, top design and smooth apps without any loadings do not even contact me. Do not contact me if you didn't download the 2 apps I mentioned above as well. Thank you