How to add border to an image with radius corners imitating the shape container element

Site URL: https://oarfish-primrose-myer.squarespace.com/

PW: Filiz

I used this CSS to create a border, but when the screensize changes, the radius changes and you can't see the black border on the top of the image.

.sqs-image-shape-container-element { 
  border: 1px solid black;
  border-top-left-radius:10.5em;
  border-top-right-radius:10.6em;
}

How can I imitate the shape that is already there, so the border adjusts itself no matter what screen size?

Thank you.

UPDATE:

https://etoile-lovers-mag.squarespace.com/

changed domain for this site...

Thank you.

What is access password...

1 hour ago, tuanphan said:

What is access password...

PW: Filiz

Try change your code to

.image-inset {
    border: 1px solid #000;
    border-top-left-radius: 15.5em;
    border-top-right-radius: 15.6em;
    overflow: visible !important;
}
.image-inset img {
    border-top-left-radius: 15.5em;
    border-top-right-radius: 15.6em;
}