How to reduce column gaps in yii/bootsrap/activeform (Yii2)? - php

Question

I am using yii/bootrap/active form and I set the layout to Horizontal
How can I reduce a gap between two columns ? I mean, where is the CSS file in yii/bootrap/activeform ?
My view code is like this
<?php
use yii\helpers\Html;
use yii\bootstrap\ActiveForm;
use yii\bootstrap\Modal;
use yii\helpers\BaseHtml;
use app\assets\myassets\InputAsset;
?>
<?php
$listData = ['1' => 'Ya', '0' => 'Tidak'];
$button = Html::button('Cancel', ['class' => 'btn btn-default btn-md', 'data' => ['dismiss' => "modal"]]);
$button .= Html::button('Submit', ['id' => 'submit', 'class' => 'btn btn-success success btn-md']);
Modal::begin([
'header' => '<h2>Konfirmasi</h2>',
'toggleButton' => false,
'id' => 'confirm-submit',
'footer' => $button
]);
echo 'Data ini akan disimpan ?';
Modal::end();
?>
<div class="jenis-form">
<?php $form = ActiveForm::begin([
'layout' => 'horizontal',
'id' => 'marketing',
'action' => ['index'],
'method' => 'get',
'fieldConfig' => [
'horizontalCssClasses' => [
'label' => 'col-sm-2',
'offset' => 'col-sm-offset-2',
'wrapper' => 'col-sm-4',
],
],
]);
?>
<div class="row">
<div class="col-md-6">
<?= $form->field($model, 'jn_byr')->textInput(['readonly' => !$model->isNewRecord,'autofocus'=>$model->isNewRecord,]) ?>
<?= $form->field($model, 'nama')->textInput(['autofocus'=>!$model->isNewRecord,]) ?>
<?= $form->field($model, 'ket_dnd')->textInput() ?>
<?= $form->field($model, 'ket_bat')->textInput() ?>
<?= $form->field($model, 'ket_tts')->textInput() ?>
<?= $form->field($model, 'k_inv')->textInput() ?>
</div>
<div class="col-md-6">
<?= $form->field($model, 'ket_battg')->textInput() ?>
<?= $form->field($model, 'ketkw')->textInput() ?>
<?= $form->field($model, 'ketrk')->textInput() ?>
<?= $form->field($model, 'tagih[]')->dropDownList($listData,['prompt'=>'<<< Pilih >>>']); ?>
<?= $form->field($model, 'deposit')->dropDownList($listData,['prompt'=>'<<< Pilih >>>']); ?>
</div>
</div>
<div>
<?= Html::submitButton($model->isNewRecord ? Yii::t('app', 'Create') : Yii::t('app', 'Update'), ['class' => $model->isNewRecord ? 'btn btn-success' : 'btn btn-primary']) ?>
</div>
<?php ActiveForm::end(); ?>
</div>