This shows the architecture of what a decentralized app would look like.
It is not too different from a typical full-stack application. You would use the Algorand SDK to write code for deploying and calling your nft marketplace smart contract. It is like an API call. You can do this directly from your frontend to make your dapp truly decentralized (no web server) or if you can implement SDK code in your web server and make API calls to those functions from the front end.
I recommend using Pyteal + Beaker for writing your smart contract and the Algorand SDK (you can choose from the 4 languages: javascript, java, python, go) to deploy and call your smart contract.
Beaker: GitHub - algorand-devrel/beaker: A framework for writing Smart Contracts on Algorand
PyTeal: GitHub - algorand/pyteal: Algorand Smart Contracts in Python
To give more info on Beaker, it is a python smart contract framework that makes your smart contract pyteal code look more like a python class and abstracts away the complexity regarding smart contract development.
The Algorand Developer Relations team is currently working on several boilerplate apps that show the full architecture. I recommend you read this article on extendable DAO. How does an Extendable DAO work? | Algorand Developer Portal
We also have Box storage coming soon which will allow you to essentially have infinite storage on your smart contract. You can read about it here: (BETA) Smart Contract Storage: Boxes | Algorand Developer Portal
I hope this helps!