Custom customer address attributes

[TestPiet]

I having trouble to show my custom customer address attributes in the frontend.

In the backend the fields are shown and i can insert / edit data of that customers address.

But in the front it wont work.

Then i editted one of the address edit phtml files and added the following

<div class="field number">
            <label class="label" for="number"><span><?php /* @escapeNotVerified */ echo __('Number') ?></span></label>
            <div class="control">
                <input type="text" name="number" value="<?php echo $block->escapeHtml($block->getAddress()->getNumber()) ?>" title="<?php /* @escapeNotVerified */ echo __('Number') ?>" class="input-text <?php /* @escapeNotVerified */ echo $this->helper('Magento\Customer\Helper\Address')->getAttributeValidationClass('number') ?>" id="number">
            </div>
        </div>
        <div class="field number_addon">
            <label class="label" for="number_addon"><span><?php /* @escapeNotVerified */ echo __('Number addon') ?></span></label>
            <div class="control">
                <input type="text" name="number_addon" value="<?php echo $block->escapeHtml($block->getAddress()->getNumberAddon()) ?>" title="<?php /* @escapeNotVerified */ echo __('Number addon') ?>" class="input-text <?php /* @escapeNotVerified */ echo $this->helper('Magento\Customer\Helper\Address')->getAttributeValidationClass('number_addon') ?>" id="number_addon">
            </div>
        </div>

Then the error was that the get function wouldnt work.
Then i added the extend of address.php data model

class Address extends \Magento\Customer\Model\Data\Address
{
    
    public function getNumber()
    {
        return $this->_get('number');
    }
    
    public function getNumberAddon()
    {
        return $this->_get('number_addon');
    }
    
}

Then still no data, but inserting and editing data is working, what i can see in the database.

What else do i need todo to get this to work, because google is helping me the wrong way.