Someone on Quora asked the loaded question - why are Germans so unfriendly - and when I read this at the crack of dawn I could not resist the temptation to answer it with one finger typing on my tablet. So here is the text below

German social behaviour is different from say, English speakers.

English is a mid-subtle language. Saving face and politeness are important, being perfect is less important. German dignity comes from merit. Being perfect is important.

1. We generally avoid direct refusals

  English: We'll see what we can do.
  German. No.

2. Specific  confirmation of informal social events.

  English: "Are you going to the pub on Friday? Probably/possibly/perhaps/maybe." (avoids No)
  German: "Yes + time/No."

3. The imperative: (which is considered abrupt or rude in English even if you have authority. Imperative sentences are normal in German.)

  English: "Could you give me that book?"
German: "Give me that book."

4. Softening the blow.

  English: "We have a small problem."
  German: "The company is bankrupt."

5. Idioms. English is full idioms. None of them have cognates with German idioms.

  English: "He was laughing all the way to the bank."
  German: "I only understood railway station. ( Ich verstehe nur Banhof.)"
 
So when a German speaks poor English they often translate their 'perfect' German sentence into an English sentence that sounds arrogant and rude.

Humour

German humour is different from English humour. English humour is based on "the reveal" German humour is usually about contrast. British English uses irony all the time German and American English (which has German cultural foundations) does not so they think you are telling the truth. When Germans are frank it sometimes sound inappropriately ironic.*
English: You're very good at sweeping the floor. - (response) I know. I learned it in prison. (Sweeping is an elementary task most people can do so I shall amuse myself at your expense by pretending I was in prison.)
Gemans and Americans now believe you were prison!

German: You're very good at sweeping the floor. (response) I took a week's training course. ( I did. To be perfect.)
British people think this is ironic.

Obedience to directives.

Speed limits.

  British English: do not go above the limit.
German: go at a minimum of 10% above the limit.
Autobahn (in case you are the one person in the known universe who doesn't know: most of the Autobahn has no speed limit.)
English: lets see if we get up to 100 mph!
German: I shall drive as fast as the maximum capability of the vehicle allows at all times even when braking.

Going places.

Every German is in a hurry to get somewhere at maximum speed possible for no obvious reason since Germans are never late. They are on a mission. Cars accelerate towards traffic jams to get there first. People on 4000 euro, 27 geared carbon fibre mountain bikes, kitted out in full Olympic competitors outfit fly past you in the cycle lane to travel the 1 kilometer from their home to their work on a perfectly flat road. 

Walks

Germans like going walks to nowhere because walking is healthy so at lunch time they walk around the block. (Causes them some difficulty in the US, where the provision of sidewalks is less than perfect!)

My German mother in law now only asks me if I want to go for a walk on Sunday if there is a destination. She knows I don't want to walk from A to A. But she still thinks it's funny!

So understand that Germans are different but no more different than any other nation and try to avoid rash ill informed judgements. Almost all of my German family and friends are polite, warm, friendly and tolerant (pretty much like all the American, French, Polish, Norwegian, Indian, Australian, Spanish, Welsh, Russian, Canadian, Italian, Greek, Texan and English people I know) and the few that are not - well they would be like that anyway even if they had been born in Scotland.

*Irony: a state of affairs or an event that seems deliberately contrary to what one expects and is often wryly amusing as a result.