New frontend dev feeling lost

I recently graduated and just got my first job as a fullstack developer — although in reality I’m only working on frontend right now.

My main stack is React/Vue on the frontend and Express/NestJS on the backend, usually building Web APIs that return JSON data. That’s the workflow I’m used to.

But the project I was assigned to uses ASP.NET MVC ABP with an older frontend style (plain HTML, CSS, and JavaScript). I had never worked with MVC before, so I spent quite a bit of time trying to adapt, and honestly I’ve been relying on AI a lot just to keep up.

My current task is to build something similar to a support/help page with a menu tree on the left and article content on the right. Sounds simple enough, but here’s the part that completely confused me:

There’s no API. No database data. No JSON structure. Nothing coming from the backend at all.

All I got was a Figma design and a pretty unclear project structure. The page also requires scrollspy behavior based on the HTML content.

This honestly shocked me because in my usual workflow, I always build the database and APIs first before touching the frontend. It makes communication between frontend and backend much easier because the frontend already understands the data structure early on.

Right now I’m just using mock data to make the UI work and writing fake endpoint functions so the structure at least looks realistic. But I feel like I’ll probably have to rewrite a lot once the real backend data finally arrives.

Is this kind of workflow normal in MVC projects or older enterprise systems?

I’d really appreciate any advice from people who’ve worked in this kind of environment before, because right now I honestly feel pretty lost.