I just added a site/language to the website and all assets are broken

[mateostabio]

My English site works perfectly, but my new French section does not.
None of the CSS or JS files are found.
The only hack I could figure out is to add this ../ before my stylesheet for FR assets because my url for french is www.website.com/fr/

Can you explain more in-depth the stamp.php and the publicRoot. I tried it but didn't seem to work. It actually broke both the EN and FR site.