Big problem with instock & outofstock variations in Woocommerce

Hello, we have big problem on woocommerce, We migrated our data from Magento 1.9.
Many products are out of stock in backend but they are visible in front.
Other products has quantity but looks out of stock.
Some products have quantity 0 but looks in stock
and the same happens on variations.. for example the product in photo, only 40 size is available
others are wrong..
This is the link of this product: https://www.topshoes.gr/komis-and-komis-kk030-gynaikeia-mpotes-mayres/