how to return vc_link in wp bakery

I am trying to create custom element in wpbakery builder in which i am adding textfield, image and url. Evrything is working fine just there is one issue in url . can anybody please help me out to solve this issue.

Below is the code i am trying :

add_shortcode( 'expert', 'expert_func' );
function expert_func( $atts, $content = null ) { // New function parameter $content is added!
extract(
shortcode_atts(
array(
'expert_image' => 'expert_image',
'title'   => '',
),
$atts
)
);
$img_url = wp_get_attachment_image_src( $expert_image, "full");
extract(
shortcode_atts(
array(
'expert_exp_image' => 'expert_exp_image',
'title'   => '',
),
$atts
)
);
$exp_img_url = wp_get_attachment_image_src( $expert_exp_image, "full");
$result .='<div class="inner__card">
<div class="expert-img">
<img src="'. $img_url[0] .'">
</div>
<div class="expert-details">
<p class="name">'.$atts['expert_name'].'</p>
<p class="designation">'.$atts['expert_designation'].'</p>
<div class="expect-experience">
<div class="expect-experience-no">
<img src="'. $exp_img_url[0] .'" alt="experience-10">
</div>
<div class="expect-experience-text">
<p>'.$atts['expert_short_desc'].'</span></p>
</div>
</div>
<p class="details">'.$atts['expert_description'].'</p>
<div class="expert-btn">';
if( !empty($url) ){
$column_link_array = vc_build_link($url);
$url = $column_link_array['url'];
$result .= "<a href='$url' class='learn-btn'></a>";
}
$result .=' </div>
</div>
</div>';
//$result = $button;
//print_r($atts);
return $result;
}
//backend
add_action( 'vc_before_init', 'expert_integrateWithVC' );
function expert_integrateWithVC() {
vc_map( array(
"name" => __( "Expert", "my-text-domain" ),
"base" => "expert",
"class" => "",
"category" => __( "Custom", "my-text-domain"),
"params" => array(
array(
"type" => "attach_image",
"holder" => "div",
"class" => "",
"heading" => __( "Choose Expert Image", "my-text-domain" ),
"param_name" => "expert_image",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "textfield",
"holder" => "div",
"class" => "",
"heading" => __( "Expert Name", "my-text-domain" ),
"param_name" => "expert_name",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "textfield",
"holder" => "div",
"class" => "",
"heading" => __( "Expert Designation", "my-text-domain" ),
"param_name" => "expert_designation",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "attach_image",
"holder" => "div",
"class" => "",
"heading" => __( "Add Year of Expirience image", "my-text-domain" ),
"param_name" => "expert_exp_image",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "textfield",
"holder" => "div",
"class" => "",
"heading" => __( "Expert's Expirience Short Description", "my-text-domain" ),
"param_name" => "expert_short_desc",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "textarea",
"holder" => "div",
"class" => "",
"heading" => __( "Short Description of Expert", "my-text-domain" ),
"param_name" => "expert_description",
"value" => __( "", "my-text-domain" )
),
array(
"type" => "vc_link",
"holder" => "div",
"class" => "",
"heading" => __( "Choose Rediect URL", "my-text-domain" ),
"param_name" => "url",
"value" => __( "", "my-text-domain" ),
"description" => __( "Add Short Description", "my-text-domain" )
)
)
) );
}

All i want is to return URL selected. i am new in wordpress.
Thank you in advance.

You are not extracting your URL so if( !empty($url) ) { wont fire, you should add all your variables to your extract code.

function expert_func( $atts ) {
extract( shortcode_atts( array(
'expert_image'  => '',
'expert_name'  => '',
'expert_designation' => '',
'expert_exp_image' => '',
'expert_short_desc' => '',
'expert_description'  => '',
'url' => '',
), $atts ) );
$img_url = wp_get_attachment_image_src( $expert_image, "full");
$url_link = vc_build_link($url);
your code...
if (isset($url_link['url'])) {
$result .= '<a href="'.esc_url($url_link['url']).'" class="learn-btn">'.$url_link['title'].'</a>';
}
your code etc...
}

Can check ( Screenshot attached )

$use_link = true;