Why is news/_entry not extending _layout?
News/_entry should definitely be extending _layout (or any layout you want to use). That's how it's setup when you download a fresh copy of Craft as well.

{% extends "_layout" %}


The CSS file should not be in the templates folder (that's only for twig templates), but in your web root which is the same folder as index.php. In your case that would probably be something like public/css/material.css and public/css/main.css Also make sure that any assets used in these CSS files are located in that folder instead of the templates folder.

Unless these CSS files are specific to the news entry template I'd also include them in the layout file.