older post nav on index.php

im trying to add a older post nav button to my main page, basically ive a made a site where the index.php of the theme is the only page you really need to look at to that extent i want every post from every category to appear on this one page, i only want to display 5 post at a time then the user uses the older posts button to load older posts is this possible or will i need to make a custom static page that gets all the post and only displays 5 at a time?

here most of my index.php i think i need to change

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