Hello Devs!

I'm a huge fan of football, and I want to understand how apps like flashscore or livescore work ( feed sources, parsing data, real time notifications, etc.). Please, point me to the right direction.

From my experience best way to learn something is, find something that works and start breaking it down

I'm sure those apps handle collecting score and stuff server side, and if they're popular enough or well funded they might get their data straight from the publishers or whoever manage the event.

If not they're probably feeding off sites that publish score online

Research RSS, most websites provide that

I agree RSS is a good place place to start. I do a lot of work with notifications - more for crisis but the same concept.

My son and I once piloted a system that provided scores a few seconds faster than the popular apps. Tested it side-by-side.
Good luck and let us know if you need more advice.

as well as the comments already made you might want to look at signalr and websockets

Check out firebase. It's a real time database.