Hi,
Your german thread title isn't helpful for sure...
I regularly work with similarity just the way you describe. Just use the auto mark function under the menu point "Action", it will only select group 2.
Be careful though, I only autodelete files that are really 100% identical in every way, the rest I sort manually.
If it doesn't work the way I described you'd have to elaborate more in which way you try it and what the result is.
Bye,
Gridwolf