WP-PageNavi posts pagination

Please can you advise- what I am missing here. I inherited the site and I am struggling to solve the pagination.

Whole navigation n this link will be changed.
I installed and activated WP-PageNavi and as advised, modified in a customised 2012 child theme – files: category.php, index.php,

function.php to register resp. function
<?php if(function_exists(‘wp_pagenavi’) ) : ?>
<?php wp_pagenavi(); ?>

….

I also replaced previous_posts_link, next_posts_link with
<?php wp_pagenavi(); ?>

Problems:
a/ Home page has 2 columns where the 2nd contains posts – I cannot get pagination for it which would be independent on the column 1 (there is no need for pagination)

b/ In the original version without WP_PageNavi and also after this installation I did not succeed in displaying all posts in menu now called “missingPosts – News”
There are about 20 posts and I would expect more pages listed here

Both a/ and b/ contain non-categorised posts.

Where should one start the debug?

Many thanks