With the help of this question I identified that I have Dutch Iris (Iris X hollandica) in my garden.
As described there the plants came out last autumn (we had a quite warm and dry autumn, following a super-dry spring in the same year). Over the winter the long thin leaves which came out survived (coldest day was -15 C) then some weeks ago some of the plants (6 of ~25) produced a stem where now the flower can be admired.
I have a couple of questions regarding the handling of these:
1) Is it normal that they already come out in autumn? Can I cut those ugly/partially dead leaves in early spring/late winter? (see picture below (taken in autumn))
2) What can I do to encourage more flowering?
3) When is the right time to multiply the plants (dig out the bulbs, stocking them, splitting them)? When do I need to put them back into the soil?