Answer:
Germans are rude / unfriendly / cold.
Germans sound aggressive.
Germans all drink beer.
Explanation:
I'm a native German and those are some common stereotypes people from other countries have about us.
We Germans often are perceived as rude or unfriendly or cold. The reason for this is, that we don't really have a smalltalk culture. People from culutres, that have a smalltalk culture (like the USA) then tend to think we're rude or unfriendly.
To many we sound aggressive or angry. This is because the German language has a lot of consonants and sounds, that may be perceived as harsh by non-German-speakers. I mean sounds like ch, sch etc.
We do have a big beer culture and the legal drinking age is 16 (for beer & wine, other alcohol the age limit is 18) but not all Germans drink and not everyone likes beer. According to statistics, Germany has a high beer consumption per capita but other countries (like Czech republic) drink more beer.
Other stereotypes are that we're very punctual and organized and good at engineering but I am not really sure why this is and how much truth is in this.