Magento 2 cannot change saleable quantity from observer

[hubit]

Hi,

I am new on Magento 2 and I am trying to update Product quantity when a user views the product, using an external API. In Magento 1.9 I succeeded in creating a custom observer. In magento 2.4 although I can change the quantity from stock in real time, the saleable quantity changes after the page refresh.

events.xml

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchemainstance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
	<event name="catalog_controller_product_view">
		<observer name="mymodule__update_product_observer" instance="HubIT\FarmakonConnect\Observer\UpdateProduct" />
	</event>
</config>

Observer.php

class UpdateProduct implements ObserverInterface
{
	protected $scopeConfig;
	protected $getSalableQuantityDataBySku;
	protected $stockRegistry;
	
	public function __construct(ScopeConfigInterface $scopeConfig, GetSalableQuantityDataBySku $getSalableQuantityDataBySku, StockRegistryInterface $stockRegistry)
	{
		// Observer initialization code...
		$this->scopeConfig = $scopeConfig;
		$this->stockRegistry = $stockRegistry;
		$this->getSalableQuantityDataBySku = $getSalableQuantityDataBySku;
	}

	public function execute(Observer $observer)
	{
		$product = $observer->getEvent()->getProduct();
		
		$sku = $product->getSku();
		$id = $product->getId();
		
		$qty = $this->productBalance($sku); //Get data from Api
		
		$stockItem = $product->getExtensionAttributes()->getStockItem();
		
		$origQty = $stockItem->getQty();

		$stockItem->setQty($qty);
		$stockItem->setIsInStock((bool)$qty);
		$this->stockRegistry->updateStockItemBySku($sku, $stockItem);
		
		echo 'test'.$qty.' '.$origQty.' '.$product->isSaleable().'<br>';
		
		$salable = $this->getSalableQuantityDataBySku->execute($sku);
                echo json_encode($salable);
	}
}

How can I achieve that?

[hubit]

No one knows how to inform the magento for quantity changes?

Is there any other way to achieve what I want?