hi, to show portfolio section please setting your page like this:
page attributes/template: list page;
page options/list type: gallery list;
page options/Enable Gallery Posts Block Mouseover Effect: check it;
btw, every post with gallery format should be assignment a featured image;
because visual composer component content only can applied to ‘default template’ and ‘static page’ template, so I think your middle section will disapear.
thank you, anything please let me known.