I found out the problem, when I tried the following expressions:
Con( "%Raster%" >= Float(2,0), 1, 0 ) -> error
Con( "%Raster%" >= Float(2.0), 1, 0 ) -> worked
So it seems that the value in the float statement has to be separated by a dot and not by a comma.
As my language on the computer is set to German, I will try it tomorrow on a computer with the language English, and hopefully the calculated values are separated by a dot.
I will let you know if it worked,
If you have any other suggestions, I would be thankful 🙂