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CMS item doesn't want stretch

Hi, i’m trying to create something similar to a top section of this page

As you can see there is a top section with an image and a list of articles.
The interesting thing is that the height of the image is adapts to the amount of lines in the right part.

I’ve tried to recreate it with a flex box, but the problem is that CMS item doesn’t want to stretch to the size of its parent.
Could someone advise anything. Thanks!