.gridbox {
  border: 2px dotted rgb(96 139 168);
  padding: 1em;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, auto));
}

.gridbox > * {
  border: 2px solid rgb(96 139 168);
  border-radius: 5px;
  padding: 1em;
  margin: 1em;
  background-color: rgb(96 139 168 / 0.2);
}

.gridbox > * h3 {
  margin: 5px 0 3px 0; /* 5px oben, 3px unten */
}

.gridbox > * p {

}