.sert-block .holder_gal {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 30px;
}

.sert-block .holder_img img{
  width: 100%;
  height: 100%;
  object-fit: cover;
}

@media (max-width: 656px) {
  .sert-block .holder_gal {
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
  }
}