Having a new portfolio on a portfolio subpage?

Site URL: https://ineharrang.com

Hi! I'm struggling with the portfolio feature. The main landing page of the website is a portfolio, a 3x3 showcase. When one of these items is clicked, you land on the sub-page. I cant for the life of me figure out how to make a new portfolio on that sub-page? Or if it can be similarly done with CSS?

I have created a new unlinked portfolio page with the sub-categories, but the way I've connected it together currently is by having a "Continue" button on the automatically created sub-page and linking the unlinked portfolio url to it, but thats not a good solution, I would greatly appreciate any help. 

Portfoilo pages cannot go into another portfoilio page or portfolio project section. They are pages not sections. Code will not change that. You coud maybe workaround that with a new section, using project sections or make your item click thu directly to  second portfoio page which could be in the unlinked section of your site of you want to keep it off the nav bar.