I dont think with css it is possible, at least not very easily. You may want to go into the wordpress editor and look for a file called ‘category.php’ within that file you will see the line “Category Archives:” it may have to be changed there. This is the prefix you see on your page. The word “News” comes from the name of the category you have the posts under I believe.
Be very carefully editing files within wordpress however. If you are not familiar with code and make the wrong change it could mess up your site. Not to mention editing files within a theme isnt best practice either. Before making changes to theme files directly, you should consider making a child theme.