If you downloaded the purchase_stock_picking_return_invoicing module, put it on the server and then restarted the server, you will solve your problems as far as I understand with these steps.
Go to Purchasing > Purchase Orders > Create in Odoo

Select a supplier and set the "Purchase Invoices Control" field to "Based on received quantities".

Enter the products and quantities you want to purchase.

Confirm the order.​

Receiving Products:

Open the shipment transaction of the purchase order you created.

Receive the products by clicking the "Verify" button.

Returning Products:

Open the received shipment transaction.

Click the "Return" button.

In the wizard that opens, enter the quantity you want to return and check the "To be refunded (Update SO/PO)" option.

Complete the transaction by clicking the "Return" button.

Verifying the Return Shipment:

Open the created return shipment.

Click the "Verify" button to complete the return process.​

Creating a Supplier Invoice or Return Invoice:

Return to the purchase order.

Create the correct invoice or return invoice according to the received and returned quantities by clicking the "Create Invoice" or "Return Invoice" button.​

With these steps, you can automatically eliminate the debit/credit deficits/imbalances in the "21080101 Provision" account and ensure the consistency of your accounting records.