.parent{
    display: grid;
    grid-gap: 10px;
    grid-template-columns: repeat(3,32.25%);
    grid-template-rows: repeat(3,33%);
    height: 1100px;
}

.pr{
  background-image: url("https://infraestructures.upc.edu/ca/principal/1-1.jpg");

  background-repeat: no-repeat;
  background-size: contain;
}
@media (max-width: 800px) {
    .parent{ 
        height: 720px;
    }
  }

  @media (max-width: 600px) {
    .parent{ 
        height: 560px;
    }
  }
  @media (max-width: 320px) {
    .parent{ 
      grid-template-columns: repeat(3,31%);
      height: 272px;
       
    }
  }


.parent > div{
padding:10px;
background-color:yellow ;


}