Use the ProperConvert app to convert your transaction files to required by your accounting software file format.
When the QIF file is created, switch to Banktivity and import created QIF file. Before importing, make sure to backup your data. To import a QIF file, select 'File' - 'Import transactions'. Then click 'Import File' and select the created QIF file.
Select a Quicken account to import.
Then click the 'Continue' button.
Pay attention that the Account name must match what you have in Quicken. Because Quicken imports directly in that account without asking anything. And if you don't have the account specified on the QIF file, this account will be automatically created. Now your transactions are imported. You can categorize, review, delete them. They are already inside Quicken. Review transactions after import.