How Can I edit css files? 

1. First method:

I read that i must make new plugin as themplate.

I add folder: "theme" in "mod"

In "theme" i created files: comopser.json and elgg-plugin.php

In elgg-plugin.php i write code like in tutorial:

<?php
        return [
                'view_extensions' => [
                        'elgg.css' => [
                                'theme/css' => [],
                        ],
                ],
        ];

I crated folder css, and there put file elgg.css

I activated the plugin in admin panel.

And this doesnt work... Whatever I write in css file it doesnt shown at the front page....

2. Secong method:

I Tried also to ovverride files by making css files in /mod/theme/views/default/elements/

but it doesnt working too