I've installed Ubuntu 19.04 from scratch after an issue with my old ubuntu installation.
I've found that now it uses GNOME instead of Unity. I like GNOME, but I have a couple of important usability issues that I assume are easily configurable, and I just don't know how to.
One of the main issues is that if I click on an image, the preview won't appear:

I am talking about the situation where you are in a list view, and click on an image, and it opens an image preview at the side of the list of files, inside the very same Nautilus window.
I tried to search for these issues instead of asking, but I've not found anything that actually got them sorted.
Please note that I've installed GNOME Tweaks.