Hi,

I made a fake page for you on staging. Namely, it’s a lighter home, because wpbakery is a true nightmare for cpu, it can break the site for a few minutes. For your info, I also have very heavy / complicated pages made with Gutenberg, when I change them, the cpu remains super cool !

Back to topic: on the page below, this is how I tried.
First, your portfolio element set to 3 columns, visible only on desktops / tablets
Second, portfolio set to 2 columns, visible only on mobile, but over-ruled somewhere to deliver 1 column.

Let me know if you need more info

Kind regards