PenciDesign replied
Hi,
I understand this issue. This issue caused by you're using slug is the same with portfolio slug. It make your link auto redirect to archive page.
Please edit this page: http://camillearnaldi.com/portfolio/ and change the slug to another - check this image
Note: When it work, if you click to portfolio items and it goes to 404 page, please go to admin page > Settings > Permalink > and click to button "Save Changes" again.
Best Regards,
PenciDesign