I was trying to give a one time donation using Paypal, but it was so slow and buggy (showing the "identify the picture" several times even after acknowledging that i got it right) and simply looping, that in the end I just had to give up. Sorry, but the interface is just plain too clumsy.
I use Paypal for paying the maintenance fee for "the Scriptwriters Toolkit" and normally it is quick and easy. I suggest you drop that "Hermes.App" crappy interface and just do a simple one, using the button creation facility provided on the Paypal website (https://developer.paypal.com/api/nvp-soap/paypal-payments-standard/integration-guide/buy-now-step-1/) . I think you can deal with the monthly/periodic payments matter by simply sending a reminder email to the doner, with the button code in the email or a link to a simple page with the button(s) on it.
Added later:
It seems that the repeated "identification" stuff is actually on the Paypal site and not the hermes app (whatever that is) The Button creation facility has an option for monthly repeated payments. So I don't know where the problem actually is.