GIVE ANSWERS - Deutsch

It's right what my previous speakers said. I just wanna add that you can see those contradictions on rare occasions, for example when you write a message to a friend or when you leave a short comment in a social network. If you use slang words or more spoken languages in forums or with strangers, they won't think you're stupid but perhaps a bit too informal. (Another fact: you can even find people who write in their dialect...)

Maybe they think you have to write it for college or something, because it depends what you write it for

While in the written English contractions are quite common, in the written German, contractions and slang are officially wrong, or at least not correct. Apart from chat, short messages and other informal texts we Germans usually don't write the way we speak, because that seems like we are not able to spell the words correctly. I guess you need to tell the people you want to write with them in slang or colloquial.