With payments received for tangible goods Paypal would request valid tracking information confirming the item has been delivered to the buyer. They can validate the tracking information online, so once it is delivered they can release the funds. IF you have received the funds for a service / virtual or digital sale or no tracking number is applicable Paypal would be unable to release the funds any sooner than 21 days.
However If you mark the transaction as processed then the buyer or sender may have the option on their account to mark the transaction as delivery/satisfied. If the buyer or sender confirms this by clicking on the "Confirm Receipt" button, funds may be released sooner ie 7 days after the buyer or sender verifies receipt. This is not always available or guaranteed. If not then sadly its 21 days.
Advice is voluntary. Kudos / Solution appreciated.