For now, it is not possible to retrieve or export a statement of your transactions in the bonsai app. The payments you have made with bonsai can be found on the account statements of your bank account to which the virtual card is linked. You can use this to link the transactions on the statement to your payment receipts.
The notification of a transaction you make with bonsai contains all the information you need for this and is structured as follows:
BONSAI-PAYMENT - date (YYYY-MM-DD HH:MM:SS) - merchant name.
With this, you can get started linking transactions to the right supporting documents.