Different Backround-Images if you choose Column

[iamye]

Hey People,
here's the way it looks:
-> bil.com/fr/Pages/index.aspx

How is it possible ?

I watched this on YouTube:
-> Elementor Pro Tip: How to Easily Create More Complex Nested Layouts

Ok, but how is it possible to change the full background when i go on one specific column ?

Help pls