Awesome post. Thank you. Interpunctuation is indeed difficult for germans here and there. Sometimes it's hard for us to read long English sentences because we miss the commas that would otherwise give structure to the sentence for us.

Btw.: It's "De->m<- Mann, der das Fenster geöffnet hat, war kalt". I guess you wanted to express that the man who opened the window was freezing. "Der" is only correct if you want to express that his temperature was low. One of those traps I guess.