As a native English speaker that used to be able to speak decent German, the one that really screwed with me was 30 minutes past/to the hour. In British English (apparently, an American girlfriend found this confusing when I said it), you can just say "half eight" and everyone knows you mean half past eight. In German, "halb acht" would be 7:30, because it's assumed to be half to instead of past. Neither is more reasonable than the other, but it definitely took me a while to get over the instinctual understanding of it. I was very late to at least one lunch