How to remove white space (margin/padding) around the content area?

I use Fukasawa theme and I would like to increase the content area in pages (here: https://www.andersnoren.se/themes/fukasawa/about-fukasawa/) and decrease the white space around it.

This is my test site (I changed the background to white):
https://mibro.webz.cz
I use Fukasawa theme with Justified gallery plugin.

My goal is a full width page like this:

This site is my inspiration:
https://www.raymassey.com/portfolio/G0000my0ARYDFHqk

I tried to do it by my self, but I am not very succesfull. Sorry for my english and thank you for any help.