.container {
   display: grid;
   grid-template-columns: 40px 50px auto 50px 40px;
   grid-template-rows: 35px 50px 30px;

   border:1px solid #ddd;
   margin-top:10px;
}

.child {
  padding: 5px;
  background: #d4e6f1;
  margin: 5px;
}

.child-1 {
   grid-column-start: 2;
   grid-column-end: 4;
   grid-row-start: 2;
   grid-row-end: 4;
   z-index: 1000;
   background: lightblue;
 }

 .child-2 {
    grid-column-start: 3;
    grid-column-end: 5;
    grid-row-start: 1;
    grid-row-end: 3;
    z-index: 2000;
    background: lightgreen;
  }