Once the product has been sold or you want to remove the notification from the service, follow these steps:
In the upper right corner of the site there is a “profile” menu, which you can click to view your information as well as the ads you have posted.
The Profile page has a “Notifications” menu under which you can see all the items you have posted. From the menu below them, you can mark the item as sold, or delete the ad from the service. Ads for products marked as sold will not be visible to others, but the details of the ad will remain in the service and you will see them under “Expired / sold”. If you press the red cross below the menu, all notification information will be deleted from the service.