.liste {
  margin: 20px;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr) );
  gap: 20px;
}

figure {
  margin: 0;
}
figure a {
  height: 100%;
  display: flex;
  flex-direction: column;
  color: currentColor;
  text-decoration: none;
  position: relative;
}
figure span {
  height: 100%;
  background: paleturquoise;
  transition: all .5s;
  overflow: hidden;
}
figure:hover img {
  filter: grayscale(0);
  transform: scale(1.1);
}
figure:hover span {
  background: white;
}
figure figcaption {
  padding-top: .5em;
}
img {
  width: 50%;
  height: 50%;
  object-fit: cover;
  flex: 1;
  filter: grayscale(1);
  mix-blend-mode: multiply;
  transition: all .5s;
}

.mainmenubtn {
    background-color: skyblue;
    color: white;
    border: none;
    cursor: pointer;
    padding:20px;
    margin-top:20px;
}

.mainmenubtn:hover {
    background-color: blue;
    }
.dropdown {
    position: relative;
    display: inline-block;
}
.dropdown-child {
    display: none;
    background-color: skyblue;
    min-width: 200px;
}
.dropdown-child a {
    color: blue;
    padding: 20px;
    text-decoration: none;
    display: block;
}
.dropdown:hover .dropdown-child {
    display: block;
}