> "Is this a web application or a smartphone one?"
It used to be a web app, but nowadays, most people use it as an app.
> "What did you have to learn, tech-wise, to be able to build it?"
At first, PHP. Then JS. I've been coding for 15-20 years now. The app is made in Ionic + Cordova. As I wrote often here on HN: End users give zero fucks about the technology. Most people (unless they're designers or coders) don't even see the difference between a native app and a hybrid one.
As a single developer, Ionic is great, because you have truly one code base for all platforms. If the apps were native, I probably couldn't do all of this by myself.
> "How long did it take you, from your first line of code until you released the first prototype?"
2-3 weeks, and then I iterated a lot with actual feedback. But: I didn't introduce a pricing model for the first couple years. It was a hobby back then. It also was a different internet. So take this with a grain of salt. I don't have experience on how to start a niche product and get paying customers from day 1.
> How did you get your first user(s)?
Through forums.
> How did you get the business idea (without details)?
A friend of mine said: "It'd be great if there was a software that could do X". It wasn't directly my own pain point, but of a friend. I didn't work in that field before, but read a lot over the years to acquire the domain knowledge.
Thanks :)