#flexCont {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
}

#flexBox1, #flexBox2 {
    width: calc(50% - 20px);
}

@media only screen and (max-width: 1000px) {
    #flexBox1, #flexBox2 {
        width: 100%;
        margin-bottom: 20px;
    }
}