Glad to have you here in the Community space, Saori
Let me help you regarding matching multiple PayPal transactions with one Sales Receipt in QuickBooks Online (QBO).
In QuickBooks Online, the ability to match multiple downloaded transactions to the transactions already entered in QuickBooks is not available. However, if you have two payments, you can apply the first payment directly to the sales receipt. After that, go to the banking page to match it. For the second payment, select the line and look for a match. The transaction should appear, allowing you to clear the remaining balance. Another workaround is to exclude the downloaded sales receipt if it has already been entered in QuickBooks.

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For future reference, please check out this resource on best practices for reconciling accounts: Reconcile an account in QuickBooks Online.
Also, I'm adding these articles that you can use as reference in reviewing and categorizing your bank transactions:
If you need any additional assistance with your transactions in QBO, please leave a comment below, and I will be glad to help you.