Cannot update stock status

Hello,

I want to update my products with the stock status (outofstock / instock) but I do not know what I am doing wrong because it does not work.

My CSV file has only two gaps. One for the SKU and one for the stock status. The SKU to identify the already existing product and the stock status to update the stock status from the existing products.
After updating, the stock status still did not change. Normaly the plugin should update the stock status or do I also need the product ID and all other gaps?

I get the CSV files from other companies where I buy the products and therefore it would be a real effort to add all the IDs and other things to the SKUs.

I am really confused and tired of all the tries..