Simple Stock Control System

Requirement:
1) for Purchase and Sales table, i can insert serial number in a single form.
2) I need to have an inventory table where it can count the onhandStock, AllocatedStock and AvailableStock and shrinkage Stock (count same product).
3) When I purchase or sales the product, the date of purchase or sales will save in the product table, so I can directly generate a report where I can know the StockIN and StockOut date.


4) I also need an Invoice Table where it can allow me to check for the invoice number, product sales, invoice date etc.
5)Serial Number must be unique
6) Warranty

Product Table:
SerialNumber, ProductName, CostPrice, Quantity, Description Supplier, Brand, Attachment, StockInDate, StockOutDate

Sales Table:
InvoiceNumber, ProductName, SerialNumber, Brand, Quantity, SellingPrice, Discount, TotalPrice, StockOutDate, Customer, Description

PurchaseTable:
InvoiceNumber, ProductName, SerialNumber, Brand, Quantity, CostPrice, TotalPrice, StockInDate, Supplier, Description

Inventory:
ProductName, OnHandStock(Purchase), AllocatedStock(Sales), AvailableStock, ShrinkageStock(Maintenance)

Maintenance:
ProductName, SerialNumber, Quantity, Description, Date_Received, DateSentToFix, Date_Returned


Other tables:
Supplier, Customer, Brand Tables, Warranty Tables

Generate Reports:
1) Stock remaining with the serial number that available
2) The stock with the serial number have been sold.

I only need a simple system only, not need to be to complicated but at least meet my requirement and user-friendly

** You may add on any idea that u wish to add
Example:
Product Name  Serial Number
HQ123            12345KH12345
HQ123            23456JT23456
SSD            KH789Y67
SSD            KH764447
SSD            KH79YH87
In Inventory:
HQ123 Onhand 2units
SSD      Onhand 3units

attached with the files that I done but there missing many parts