The Community has your back, melania.
I'd be delighted to help with your question about stopping automatic download of transactions in QuickBooks Online.
You can disconnect your online banking within your QuickBooks account to get rid of the bank data downloading automatically. Before doing so, please make sure to add transactions from the For Review tab.
Once done, you can proceed with disconnecting your bank account:
I'm adding the screenshot for your reference on this:
Please be sure to let me know if there's anything else I can do for you related to QuickBooks banking. I'm always available to help.
Thanks for chiming in on the thread. It doesn't delete transactions added to the register. Things that would get deleted or lost are the ones in the Review tab. Please let me know if you have any other questions. I will be more than happy to help! Be safe.