Hi @Adi,
Could you please explain a bit for the lookup fields configured for those two lists?
If the ProductName lookup column under Receipt only reference single column (Value should be unique) in Product list, then we could take a try with the following way to update the related Stock:
1. First the SharePoint trigger "When a new item is created", set with the SharePoint site URL, and the Receipt list,
2. Add a SharePoint Get items Action, specify the Sharepoint Site URL, and the Product list,
3. Add a condition, choose the ProductName Dynamic content generated from Get Items as the Object name, and the ProductName value dynamic content generated from "When a new item is created" as the value,
4. Under the Yes part, select the update item, use the ID generated from "Get items" as the Item ID, then update the corresponding column with the data you want
A screenshot for reference: ("Title" here should from Product list->Get items action, "Lookup value" should from Receipt list->When a new item is created trigger )
If you need any further question on this, please post back.
Regards
