Hello Kathrin,
Since you asked for CC,I find all three images to be a bit flat and lacking in contrast. A bit underexposed perhaps, especially in the first. I played around very quickly in photoshop on that one, and to my tastes found a 30 second bit of photoshop made the first shot really pop.
A bit higher on the flash output, and I think you'd have it nailed, and then a touch of contrast in post.
BTW, there is a private members only picture subsection on OSP that you might want to use for future posts of models like Svetlana. Some people around here get their knickers in a knot when they stumble upon photos like these.

)
Thanks for sharing. Hopefully you'll get some more feedback as well.
Chris.