styles.css

#billing_street_number_field {
    -webkit-flex-basis: 100% !important;
    -ms-flex-preferred-size: 100% !important;
    flex-basis: 30% !important;
    width: 30% !important;
    float:  left !important;
    clear:  none !important;
}


#billing_address_1_field {
    -webkit-flex-basis: 100% !important;
    -ms-flex-preferred-size: 100% !important;
    flex-basis: 65% !important;
    width: 65% !important;
    float: left !important;
    clear: none !important;
    margin-right: 5% !important;
}
@media screen and (max-width: 380px) {

    .woocommerce-checkout div#billing_street_number_field,.woocommerce-checkout #billing_address_1_field,.woocommerce-address-fields div#billing_street_number_field,.woocommerce-address-fields #billing_address_1_field {
        -webkit-flex-basis: 100% !important;
        -ms-flex-preferred-size: 100% !important;
        flex-basis: 100% !important;
        margin-right: 0 !important;
        width: 100%% !important;
        clear: both !important;
    }
}