.sv-check-item {
    appearance: none;
    -webkit-appearance: none;
    border: 0.21em solid;
    border-color: $main-black-color;
    height: 1.7em;
    opacity: 0.5;
    position: relative;
    width: 1.7em;
}
.sv-check-item:checked {
    opacity: 1;
}
.sv-check-item:after {
    display: none;
    left: 50%;
    margin-right: -50%;
    position: absolute;
    top: 50%;
    transform: translate(-50%, -50%); 
}
.sv-check-item:checked:after,
.sv-check-item:hover:after {
    display: inline-block;
}
.sv-check-item:focus {
    box-shadow: 0 0 0 0.21em white, 
                0 0 0 0.28em#19ab8d;
    outline: unset;
}
.sv-check-item {
    appearance: none;
    -webkit-appearance: none;
    border: 0.21em solid;
    border-color: $main-black-color;
    height: 1.7em;
    opacity: 0.5;
    position: relative;
    width: 1.7em;
}
.sv-check-item:checked {
    opacity: 1;
}   
.sv-check-item:focus {
    box-shadow: 0 0 0 0.21em white, 
                0 0 0 0.28em#19ab8d;
    outline: unset;
}
Delete unnecessary styles in check-item block
Delete unnecessary styles in check-item  block
