The Question and Answer section for The Boy in the Striped Pajamas is a great resource to ask questions, find answers, and discuss the novel.
One train was a nice passenger train for Germans. The other train was made up of cattle cars to transport Jews.
I suppose that would depend on what foreigners you are referring to. Kotler is not a major character in the book so any answer would be speculative. Kotler, being a brash Nazi, would have a very narrow definition of what he might find acceptable....
Bruno's father was Kotler's commander so Kotler gave him respect. Kotler's identity was being a Nazi Soldier so he would have approved of others like him.