How can I know that my stock is low?

You can choose to be notified when your stock is about to finish.
To do that, please click on the circle on the top right part of the dashboard and then on "MANAGE PROFILE" to access your account settings:

Then, please click on "SETTINGS" and you will land on the following page. After, please check for the "Low Stock Alert" section:

From here, you can choose the amount limit that you prefer so once your goods stocked in the virtual warehouse reach and go below this value, you will be notified via email. When one of your items will reach that amount, you will receive a notification.
Once, done, please click on "UPDATE".