A gift of poison
Take the word gift – if someone presents you with it, they’re either trying to impress you or kill you. While an English person would be delighted to receive a gift, a German speaker will soon realise they’ve been poisoned and hope that someone will call an ambulance, perhaps even shouting “Ich habe Gift bekommen!” which an English person may translate as “I am becoming a present” and think that you’re preparing for a fancy dress party, hence the green face.
I did a failure…
OK, this is a silly example. But you’d be surprised how prevalent common mistakes are. “Seit” may mean “since”, but “ich wohne seit zwei Jahren in Zürich” is “I’ve lived in Zurich for two years”, not “since two years”. “Machen” is both “make” and “do”, which is confusing because the temptation to say “we make a holiday” or “I make a photo” or the classic “we make party” is just too strong. “Bekommen” (get, receive) vs “become” (werden) already mentioned above also has a few more tricks up its sleeve. Like “ich bekomme ein Baby” – “I’m getting a baby” – which sounds rather biblical, and “ich bekomme ein Steak” for “I’ll have the steak”. From the German perspective, Pinocchio does not “become/bekommen” a boy, but “wird ein Junge”, so the confusion goes both ways.
One of my favourite false friends is the word “Glück”, related to “glücklich”, which seems to have tricked German speakers into thinking that being lucky and feeling happy is one and the same thing. It’s fitting because these moments do make me smile: a speech that starts with “I am so lucky to be here” makes me think the person has overcome a great feat to reach this moment, while slogans like “We make you lucky!” conjures up images of winning the lottery.