What i get is follwong (correct me if i am wrong) : You have an article which you can configure or classify. You read a certain characteristic which holds the Area in squaremeters.
Since characteristics values get stored in CHAR, you want to convert it to a number, so that you can calulate with it, or make a nice output format.
So your only problem is the conversion from char to number, right?
you can simply move the char value to a number variable e.G.
DATA: lv_char type c length 30 VALUE '3.123,33'.,
lv_number type kbetr.
lv_number = lv_char.
If the char value is a valid number it will work, otherwise it will DUMP.
to be a bit more sure that it will work you can eliminate those thousand seperators, and make sure the decimal is a comma (yeah thats the internal format).