I'm very new to drupal, so I apologize if this is a dumb question.

I'm trying to set up a drupal theme to use for my webcomic, however I'm struggling with the logic for the page navigation.
How do I point to the next/previous and first/last items? I found some resources using php, but I don't know where it would go in the code and I'm not sure if I should be setting up the page navigation as part of the custom theme.

this is not the drupal theme (though I do hope to get it here) I started in react before I abandoned my original idea of hooking a react front end to a drupal back end and instead just decided to do the whole thing in drupal

The goal is for each page to have buttons at the bottom that point to the next comic page, previous comic page, first page, and latest page (which is also the home page). I saw a post from 6 years ago with a similar question, but the top comment only said to 'theme it in HTML/CSS/JS' first, but I'm stuck on how to set up the page logic, which would be interacting with the cms?
I set up my project with composer and am currently using ddev if that is relevant.