If not difficult, could you estimate the complexity of creating a service?

Question

Electronic commerce

Good day! I apologize in advance if my question seems abstract, unfortunately I do not have knowledge in the field of programming ... and thank you all in advance for your answer!)
Attention question:
I ask you to evaluate the complexity of creating a service (if possible, so to speak, then a test version), I will try in order. The user passes authorization (two categories of users - supplier, customer), after authorization enters the personal account (the supplier in the personal account can select the category of goods that can be delivered and enter its parameters, respectively, the customer selects the product he is interested in buying), when In this case, the customer selects the product according to key parameters i.e. for example, goes to the "Office Paper" tab and enters its parameters. sees the types of paper that are suitable for the parameters, clicks on the selected one and sees the suppliers, then goes to the supplier's page within the service and makes a request that comes to the supplier's personal account, respectively, the latter sends a response to the customer's personal account.
So far so... I hope I wrote it in an accessible way... and yes, it should be possible to exchange files within the service, between the customer and the supplier.
Thank you very much!!!

Answer 1

Tell me, what do you include in the creation of a service? Only functionality, or also design?
On any modern framework, this is implemented in 2-3 months, depending on the features, it is easier to immediately divide the development stages in stages and, accordingly, first launch the version for suppliers, test the service, refine it, and then drive customers there. Users are still not 2 roles, but at least 3 (+ admin), admin panel as a separate module, products, parameters of products, relation of products with parameters, based on these links, dynamic forms for editing different products. Orders, their statuses, resolution of disputes, how payments are made, through the service or bypassing it. There is not enough information to give a sober assessment, design / layout / development / server setup for the project. In my experience, I can say that such services are raised by a team of a month in 3. For one layout, there may be such wishes of the customer,