.speaker {
	box-shadow: 0 0 0.5rem 0 rgb(0 0 0 / 20%);
  background-color: #fff;
  width: 253px;
  position: relative;
  overflow: hidden;
  transition: all .4s;
}
.speaker:hover {
transform: translateY(-0.5rem);
}
.speaker:hover .photo_speaker {filter: grayscale(0%);}

.container_speakers {
	display: grid;
	grid-template-columns: 1fr 1fr 1fr 1fr;
	grid-gap: 40px;
}
.photo_speaker {
	display: block;
	height: 278px;
	margin: auto;
	margin-bottom: 20px;
	background-size: cover!important;
  filter: grayscale(100%);
  background-position: center;
}

.photo_speaker::after {
  position: absolute;
    content: "";
    -webkit-transform: translateX(-50%);
    transform: translateX(-50%);
    bottom: 0;
    left: 50%;
    width: 400%;
    padding-top: 400%;
    border-radius: 50%;
    background-color: transparent;
    box-shadow: 0 0 0 100px #fff;
}

        img {
            width: inherit;
        }
        .about_speaker {
            text-align: center;
            height: 132px;
          	position: relative;
        }
        .name_speaker {
            margin-bottom: 10px;
            font-size: 18px;
          	font-weight: 600;
        }
        .description_speaker {
            font-size: 14px;
        }

@media screen and (max-width: 1200px) {
.container_speakers {grid-template-columns: 1fr 1fr 1fr;}
}
  @media screen and (max-width: 991px) {
.container_speakers {grid-gap: 15px;}
  }
@media screen and (max-width: 910px) {
.container_speakers {grid-template-columns: 1fr 1fr;}
}