@apecity
In Publii Simple theme settings: Theme > Theme Settings > Custom settings > Layout > Hero section, the default value is probably 80vh. You could probably experiment with changing that value — perhaps try 40vh or something similar.
Though do remember, the Simple theme is intentionally designed to be simple in layout. So the short answer to your question is:
– Add a suitable background image to each page.
– Add the other information for the page (check the theme settings).
– Add some text and other content in your articles.
Check out the various example page on the Simple theme demo: https://demo.getpublii.eu/themes/simple/
If the above options don’t work for you, in addition, if you wanted to avoid making direct changes to the Simple theme itself, you can can find more exotic, different, or flexible layouts at: https://marketplace.getpublii.com/themes/
