:root{
    --size-arrow: 12px;
}

.container_form > .row > span > select{
    width: 100%;
    padding: 0;
}
.container_form > .row > span#arrow_for_select{
    position:relative;
}
.container_form > .row > span#arrow_for_select:after{
    content: "";
    width: var(--size-arrow);
    height:  var(--size-arrow);
    z-index: 1;
    border-right: 2px solid black;
    border-bottom: 2px solid black;
    display: block;
    position: absolute;
    top: calc(50% - var(--size-arrow)/1.5);
    right: calc(0px + var(--size-arrow)/2 + 8px);
    transform: rotateZ(45deg);
    pointer-events: none;
}