scrolling menu changing from another scrolling menu

Hello guys,

I've been on this for days and haven't found a solution. I want a scrolling menu depending from the choice of an other :

public function getClientInfo(Request $request)
{
    $customerInfo = Customer::find($request->customer_id);
	$ClientContactsInfo = ClientContact::where('client_id' , $request->customer_id)->get();
	return response()->json(['success' => true, 'response2'=>$ClientContactsInfo, 'response' => $customerInfo]);
}

Javascript :

<script>
    $(document).ready(function () {
        $('#client_id').trigger('change');
    })

    $(document).on('change', '#client_id', function () {
        var save = '{{url('/')}}/admin/inquiry/getClientInfo';
        $.ajax({
            url: save,
            dataType: "json",
            type: "Post",
            async: true,
            data: {customer_id: $(this).val(), "_token": "{{ csrf_token() }}"},
            success: function (row) {
                $('#client-email').val(row.response.email);
                $('#client-phone').val(row.response.phone);
                $('#client-address').val(row.response.address);
                $('#agency').val(row.response.first_name);
                $('#agency_address').val(row.response.address);
                $('#gestionnaire_id2').val(row.response2.email['0']);					
			},
            error: function (xhr, exception) {
                alert('There is some error in system 1');
            }
        });
</script>

and HTML :

																							<select id="gestionnaire_id2" class="form-control select2">
																							<option value=""</option>
																							</select>

Would you have a solution ?