Child theme and function-core.php file

Hi,

The alteration i would like to achieve is below.

I want to change lines 359-361 {Really just line 360}

of

mysite/wp-content/themes/kleo/kleo-framework/lib/function-core.php

from

elseif ( is_category() ) {

            $output = __(‘Archive for category:’, ‘kleo_framework’) . ” ” . single_cat_title(”, false);

        }

to

elseif ( is_category() ) {

            $output = __(”, ‘kleo_framework’) . ” ” . single_cat_title(”, false).” – Our Posts”;

        }

This alteration  can, hopefully, be put in a child theme.

But up to now the child theme file does not get recognised (at kleo-child/kleo-framework/lib/function-core.php)