Alas, I only see the HTML skeleton of your project and not the styling.
Your CSS stylesheet (And some other files) is not properly connected in your .html file.
It should be something like this:
<link rel="stylesheet" href="./stylesproduct.css">
This is called a relative path. Read more about it here: HTML File Paths
You were referencing the file from outside your project directory like:
/Users/fabiennehalloin/Desktop/HTMLChallenges/product-preview-card-component-main/stylesproduct.css
Stay within your project directory while referencing files.