how to edit pages?

https://codex.www.ads-software.com/Pages#Page_Templates

Thanks, but this doesn’t help me. My theme doesnt have a page.php file, so I guess WP uses the default. That file doesn’t call for comments at all, but they do show up on the page, see: https://www.boneless.nl/introquiz/

Where can I find the file that determines the look of a page?

The file you need to edit is:
layout.css
and
the style sheet that controls graphics the theme style sheet(layout.css controls layout)

Since WP is an xstandard app the presentation and content are separated.

To create pages
If you have installed the latest version then:

Login
Go to “Manage”
Go to “Pages”
Click on “Create a New Page”

Your Done!

Hope this helps