Loop not working

I try to create some columns in a loop, but for some reason the loop is creating only one column. What am I doing wrong?

I attached the csv file and the workflow.

Thank you!

You must use the Loop End (Column Append) node.

Best, Iris

Great! Thank you, Iris. That fixed my problem. But, now I see that in addition to the new columns I want to add, the existing columns are duplicated as well. What changes should I make to my workflow so that I add only the new columns?