Display a single category in blog section

I have been struggling with a problem, I have a webpage running on WordPress, most of the things work as expected, except one: in the blog section page (the one that is configured in settings/reading -> Posts page), all posts are shown. I have a specific category that should be presented there, but I don’t know how to alter the loop to work as expected. Here´s the code of the index page:

How to Get The Excerpt of the page that displays Blog Posts

I use a static page (Blog) to display the latest posts. I want to show the excerpt of that page next to the title. However, wen I use wp_kses_post( get_the_excerpt() ), I get the excerpt of the latest post from the post archive loop. I also tried with wp_kses_post( get_the_archive_description() ) but it also does not seem to work.. Any idea how this can be done?