It looks like you are using a list box with an additional expression. This is similar to having a chart with dimension schlagwort and your expression, and you will see both columns.
You can use an expression instead of your field in the list box (choose <expression> from the field selection drop down in list box general properties), but it is better to create a new field in your load script that does the replace (or replace your original field with your modified):
replace(...) as schlagwort,
If you want the list box solution:
=aggr( replace(...), schlagwort)
[You'll need to use your complete replace expression of course].
Hope this helps,