Hello,

I have added a custom class for the “Portfolio” element: https://prnt.sc/W0A0SWlOncHv

So after that, you can use the below code for making the portfolio item circles.

.custom-portfolio .portfolio-entry .entry-header{
    border-radius: 50%;
}

https://monosnap.com/file/LkvQQlLlZcaB7et8lgrqqI21hQ5jiq

Kind Regards