Change point in String to comma

Hello,

I want to create a table with the column names in a certain row. For that i used the column name extractor to add the column names to the top of my table. The problem is, certain column were in number(double) but are now in ? because the column name is a string. The numbers that were type casted from double to ? have now a decimal seperated by a point (.). However I need the decimal seperation in the final excel to be a comma (,). That is why i wanted to use a Number to string node to cast the columns i need to string. And with a string manipulation node i wanted to change the points to commas. Since the first 30 rows of my table are empty the replace string method does not seem to work and when checking if the rows are empty is does not seem to work.