I have been able to configure the template but I cannot find the "single Portfolio" part. I can't understand if it exists to create it with the FrontEnd editor or if it's custom made.
That is project page. You can create new and using WBBakery elements to build the layout:
okey, thank u.
Then, when I open the essential grid, where I can change the images from Grid 3 Columns?
You can set up the grid style in here: https://prnt.sc/r7pacd