Hi Jarvis,
In order to get the payment result immediately from PayPal you must configure the PayPal Instant Payment Notification (IPN) URL in the Setting application under E-commerce > Payment gateways > PayPal. The default URL is: ~/CMSModules/Ecommerce/CMSPages/PayPalIPN.aspx
Additionally check that you have defined the preferred order status for successful payments by setting the property Order status if payment succeeds in Store configuration application under Payment methods > [edit PayPal payment method].