main{

 margin-left: 10%;
 margin-right: 10%;
}
.bilder{
    display: flex;
    flex-direction: row;
    text-align: center;
    justify-content: space-between;
    flex-wrap: wrap;
}

.bild {
    margin-top: 1em;
    width: 45%;
    background-color:rgba(128, 128, 128, 0.511) ;
}
.bild img{
    width: 100%;
}
.bild p{
    font-size: 2em;
    margin-top: 0;
    margin-bottom: 0;
    color: black;

}
.bild a{
    text-decoration: none;
}
.bild:hover{
    background-color:rgba(128, 128, 128, 0.909);
}
@media  screen and (max-width: 900px) {
    .bilder{
        flex-direction: column;
    }
    .bild{
        width: 100%;
    }
}