The problem seems to be the same as in the earlier post. There are new-line characters in the column names, e.g. “Ersatzteilart:\nWerkzeug A”. One can see it by saving the data in csv format directly from Excel and then opening the file with a text viewer.
If I read in the file sample that you have provided with Excel Reader and then rename columns with the solution suggested by @nemad here I can successfully run Backward Feature elimination