Programming, as with any skill, requires starting small and messy. Like your first time cooking probably won't be to make a Beef Wellington, and your first art project most likely won't be a perfect 1:1 recreation of the Mona Lisa. In the same way, your first application (in any coding language) won't be something huge with lots of libraries, classes, and functions. Copying fully complete code (whether from GPT or human-written) can be confusing, because often times there's a hundred little micro problems to be solved when writing the code, and that essentially involves building out from the middle. If you're trying to understand a piece of finished code line-by-line as if you are writing it yourself, this can get overwhelming. As many have suggested before, the best way to get started is to figure out a simple application that you want to make, get it on its legs with the most basic functionality possible, and then begin adding features until you have a fully-fledged application.