The 3D secure flow requires a redirect to the bank's window, to simulate that, send the amount of 55.3 in any currency, the response that will be given will be ReplyCode=553 which means Pending transaction, the response will include the Pending transaction ID along with the URL to redirect the window to.
Remember you will need to URLdecode the URL, in the 3Dredirect field,before redirecting to the URL.

For 3DS2 transactions additional params are required in order to process the transaction with most of the acquirers - please be sure to pass the information via the requests.