Is it ok if I use a hand-created file of german holidays (official/semi official, etc.)?
Do we know this is in Germany? Do we even know it is in a single country? Thanks 
It is ok to use holidays. We have added this note to the problem description.
Schneider Electric is headquartered at France and serves (more than) 10 countries. Assuming the dataset is from Germany and generating holidays might give you unexpected results.