Hello @juli7070
The Blocksy Companion plugin provides some header features such as additional elements for it and the ability to turn it sticky or transparent.
Regarding the global.css file, the plugin is the one that actually generates it. If the plugin is not installed, every style is placed inline on the page.
And regarding Gutenberg, you can run into other issues such as styling the elements on page. I’m really sorry about this one but Blocksy is a Gutenberg-based theme and using legacy technology can have adverse effects. I can also say that Blocksy is compatible with other popular page builders, such as Elementor, so you may want to use something like that?
Hope this helps!
Thanks.