ZUKI: previous / next post of the same category?

Hi!
Using Zuki and trying to solve the following:

Description
My menu items refer to categories. I.e. clicking on a menu item (=category) takes me to a space where there’s a grid with posts of that category. Clicking on a grid item takes me to a post of that category.

Problem
The previous/next post links (at the bottom of the post) offer posts from various categories, not just from the category I am currently reading. So, the post I am reading is in Category X, but “previous post” offers a post of Category Y and “next post” offers a post of Category Z. (Messy.)

Question 1:
Is there a theme-wide CSS code snippet to keep the previous/next posts within the (same) category as the post I am currently reading?

Question 2:
Is there a theme-wide CSS code snippet to remove the “previous/next post” links, together with the arrows and ornamental line separating the post from the footer, from the entire site?

Many thanks!
Christos