Please be the Software Dev friend I’ve never had and help me out

Hi guys! As per the title, I've never had any software developing-savvy friend whom to ask even the most basic questions on programming etc.. Hope I'll find a kind soul here ahah

So the thing is I'd like to start learning how to code to build my own website (with chat, uploading capabilities, maybe even accepting payments on it) and I am very happy so spend some $$$ on Udemy/Coursera but I have LITERALLY no idea of which programming languages I should begin learning.

The question is this, to build something like that, what would I need to focus on? Online I found languages like Javascript and React, but what about the back-end? Also how do these websites "connect to servers" (like AWS or Google Firebase), like how do you make your website communicate/connect with these servers (on which to store data/send requests/ etc…)? Do you use Python to connect to the servers? Or is it something more complicated?
Feel free to roast me for my super general (and probably stupid) questions, but also answer some lol

Thanks in advance guys!