Thanks for posting to the Community, @finance133.
Currently, we're unable to import PayFast payments to QuickBooks Online (QBO).
Since these payments are deposits, I'd suggest getting these transactions directly from your bank via WebConnect and then import the data to QBO. You can use this workaround to import payment transactions.
For the detailed instructions, you can follow the steps through this article: Manually upload transactions into QuickBooks Online.
Once you have uploaded the data, you can now add, match and categorize them in QuickBooks.
For API integrations, you can check the PayFast web page if they can customize integration with QuickBooks Online.
Feel free to tag me (@Jovychris_A) if you have additional questions. I'm always here to help. Take care!