it worked perfectly, thank you very much !

Hi,
thank you for the reply but I manage to correct the problem myself. (But I see another reclamation for bad resizement on smartphones with fullscreen featured image so I’ll explain what i did.)
I think there is a lack of @media style info for smartphones when you use parralax post featured image in a boxed website (with background)

here is what I did to correct the cutting of the parallax featured image on smartphones, I don’t know if it’s the best we can do but it worked, I’ve added that to the CSS :

@media (min-width: 200px) and (max-width: 767px) {
  .td-boxed-layout .td-big-slide-background {
    width: 100%;
  }
}