#GridTop {
  display: grid;
  grid-template-columns: 50% 50%;
  grid-template-rows: 50% 50%;
}

#GridPicture1 {
  max-width: 100%;
  grid-column: 1/2;
  grid-row: 1/2;
}

#GridPicture2 {
  max-width: 100%;
  grid-column: 1/2;
  grid-row: 2/3;
}

#GridPicture3 {
  max-width: 100%;
  grid-column: 2/3;
  grid-row: 1/3;
}