It would be very nice if you'd said 'please', guest, but I'll try to help you.

You can cut the flower stems down to the base as soon as all flowering has finished. You may see a little new growth this year, but more likely in the spring. It's wise to take precations against slugs and snails then, as they really enjoy a 'munch'.

Let the leaves die back naturally though Guest to help feed the roots. And yes, please and thank you go a long way on this site.