How do I begin on a data input, recording, and graphing program? (That I might port to a website)

I'm currently prototyping a system where i could get live data sent from my Pi, and graph the results in real time.

I'm very new to all of this however all my focus is currently set in even seeing if its possible to do this. Here is a plan of the program I want to create before I worry about networking my Pi:

1. accepts a value X from my own input (like on a slider of 0-1000)
2. record X onto a table every 5 seconds
3. Table includes, time, date, X
4. Display a line graph of the data X through time e.g. (last 30s, 1h, 12h, 1d)
5. Turn on and off

Prefferably, all of this would also be able to be displayed on a phone as well (perhaps all of this could be done on a website/page? )

I do not know how to begin, I don't know where or who to ask from help from. I'm not even sure if this is the right place but I'm pretty lost and clueless atm and any help would be appreciated on where i should start from what language or what I need to even get this done. All I have is a background in Python, C++ and some html and css but nothing. Perhaps there are sugestions of communities like discord servers as well where I could talk with people and stuff?

Again, thank you~