Advice on how to approach website development

I'm new to this forum and new to web design. I'm looking for some advice. I think I'm in the right place but my question might not be specific enough.

I have many years of experience as a software engineer (C, some C++, some python) on various large and small devices (e.g., patient monitors). But I don't have any web development experience.

I want to build a website to help users learn a specific skill. The heart of the website would be a single web page, with 4 inter-related windows, where a change in any one window would be reflected in the other windows. Each window would be a mix of text and fairly simple graphics. I envision the user staying on this single page most of the time.

Initially I am just looking to build a prototype for user testing purposes - ultimately there might also be a way for a user to login, to save some state related to their progress, maybe an associated blog, and it might be good to be mobile-friendly - but this is all 'down the road' if the feedback from the prototype is reasonable.

I know this is all pretty fuzzy so sorry about that. I have reviewed some of the website builders offered through popular web hosts (e.g., squarespace, weebly), but I don't think they will support the interaction between multiple windows on a single page that I'm looking for. As I said I'm a newbie to web development, but it looks like there are some interesting web frameworks (e.g, Django) that might make more sense for someone with a programming background to use for what i want to do.

Does anyone have any advice on what website development tools to look at for this type of website development, for someone with a strong (non-web) development background?

Thanks