Hi Maik,
The way described by my colleague will let you set the fullwidth option to the global container, which is equally applicable to Header, Footer and Content.
You can have the similar structure, if you select the template Blank No Container|Header, Footer, and set fullwidth, and latter set the equal padding to the left & right of the Row element.
It can be easily achieved if you are using the Header & Footer builder to customize the header and footer as per your need, even the fullwidth. But that is exclusively available with the Pro, not the X, which you are using.
In this regards to get customizable headers, I would suggest you upgrade into the Pro theme, please go through the process here: https://theme.co/docs/converting-from-x-to-pro
Thanks