is it possible to add a status "Return Item" in this database, which means this action will return the item in inventory plus the customer order will become zero. (as if he returns the item to the shop)
You are playing with fire if you start adding things back into the inventory. It could very easily get out of control and you end up with corrupt data, as in you don't have a true representation of the stock numbers.
These sort of problems existed way before computers and databases. The original solution was an accountancy system.
The Northwind example database demonstrates an order, with line items, basically imitating an accountancy process.
When you return something to a company they issue a credit note. This records the fact that you have returned the item and allows the processing of a refund. With regard to the inventory, you just look at the items listed in the credit note table and this tells you what items have been added back into inventory without messing around with the inventory quantities.
Caveat:- I'm not an accountant, I know there's at least one accountant here who might be able to advise you on how to handle accounting procedures in an MS Access database.