impossible to create different pages/post, #2

Hi again,it seems impossible to create different articles/posts with colibri on brite theme. Overall, it seems that Colibri is just there to slow you down :/

I read on the documents that

You can make changes either to the style and appearance of these pages, or to the content of the respective pages. To edit the content of the blog pages, you need to go to the WordPress admin dashboard, choose the blog/single post page you want to change and click “Edit” (please note that you have to click “Edit”, and not “Edit in Customizer”). To edit the style and appearance of the blog pages, you can make the changes in the Customizer.

Note: If you want to make changes to content, within the Customizer, the changes you’ll make too one post will apply to all posts!

however, this seems not to work: my blog template (edited with colibri) is empty, but when I edit a post on the classic editor through the admin panel, nothing is visible on the published post. Is there a solution for that?

The page I need help with: [log in to see the link]