You could do that by changing:
.hikashop_product_left_part {
text-align: center;
float: left;
width: 50%;
}
to:
.hikashop_product_left_part {
text-align: center;
float: left;
width: 60px;
}
and:
.hikashop_product_right_part {
border-left: 1px solid #DDD;
float: left;
padding: 10px;
margin-bottom: 30px;
}
to:
.hikashop_product_right_part {
border-left: 1px solid #DDD;
float: left;
padding: 10px;
margin-bottom: 30px;
width: 100%;
}
in the front end CSS file of HikaShop via the Display tab of the configuration.