How would I create a webpage that allows me to write anywhere, JS, Html, Css

Example Image (Photoshop)

What would be the best way about making a web page that allows me to click absolutely anywhere and type, hopefully overwriting the text next to it, such as what many IDE's do, where when you type it overrides the following text.

I was hoping to also have the file once finished upload to my server, that way its saved for later. So far i'm somewhat stumped, i'm aware of somewhat what i'm doing, just that nothing is occurring to me of what I could do. (Also i'm somewhat new to java-script, I only know the basics.)

I know this is a lot to ask but i'm trying to learn, my discord is Woop#0001 if you'd like to chat and help me understand what i'm supposed to do.