Create block and use it in template - Error filtering template: Invalid method

I created a block and a template. I call the template in a CMS site.

Block:

\app\code\Fekete\Newsletter2Go\Block\Form.php

<?php
namespace Fekete\Newsletter2Go\Block;

/**
 * Dashboard Customer Info
 *
 * @api
 * @since 100.0.2
 */
class Form extends \Magento\Framework\View\Element\Template
{
    public $helper;
    /**
     * Constructor
     *
     * @param \Fekete\Newsletter2Go\Helper\Data $helperData
     * @param \Magento\Framework\View\Element\Template\Context  $context
     * @param array $data
     */
    public function __construct(
        \Fekete\Newsletter2Go\Helper\Data $helperData
        ,\Magento\Framework\View\Element\Template\Context $context
        ,array $data = []
    ) {
        $this->helper = $helperData;
        parent::__construct($context, $data);
    }

    /**
     * @return string
     */
    public function test()
    {
        return __('Hello Developer! This how to get the storename: %1 and this is the way to build a url: %2', $this->_storeManager->getStore()->getName(), $this->getUrl('contacts'));
    }

}

Template:

\app\code\Fekete\Newsletter2Go\view\frontend\templates\partials\subscribe\form.phtml

<?php
/**
 * @var \Fekete\Newsletter2Go\Block\Form $block
 */ 
    echo $block->test();
?>

I call the template in the CMS page like this:

{{block class="Magento\Framework\View\Element\Template" template="Fekete_Newsletter2Go::form.phtml"}}

Result:

Error filtering template: Invalid method Magento\Framework\View\Element\Template::test