Posts per page, offset, pagination mystery

Can you display a few posts on one page, then a different number of posts on page 2, page 3, etc.

I spent a day searching, googled and googled every combination of words and even found other posts saying they did the same thing; still to day there is not answer.

Can a hero answer this?

I have a blog category for which I display a very customized “home” page. I display a few posts, in different columns of different sub-categories. And I do a “do not duplicate” trick so they won’t be on the next page. I want the next page to display the rest, but more per page.

Anyway, to put it simple: How to display only, say 5 posts on the first page, and 10 on the others? If you add a custom posts_per_page in function.php for that category only it won’t work. Say you set:
Page 1 : 5 posts per page (posts 1-5)
Page 2 : 10 posts per page. (posts 11-20 !)
Page 2 will start at the 11th post because it thinks page 1 displayed 10 posts. Posts 6-9 are skipped.

So I tried making some code (I’m not a coder) by counting the page I’m on, multiplying the number of posts per page, then subtracting to try to show the post where I should be at. Using offset.

I made a function in function.php using pre_get_posts that does something similar to this (not the actual code or calculation)

——
If (this category is not paged){
$query->set (‘posts per page’, ‘5’)}
If (this category paged){
$page = thispagenumber
$new_offset = (page * 4) – 5
$query->set (‘posts per page’, ‘5’)
$query->set (‘offset’, $new_offset)}
—-

Number of posts per page work, but it still skipped posts. Problem is, Offset doesn’t work with pages from what I understand.

Some have suggested solutions but these may break on the last page and give a 404.

Is there a non-plugin clear solution to this?