German empire's language:
German language was spoken in German empire and first years of 20th century, was same as this German language that is spoken now?
There have been some changes. Some words are not used anymore, other words (like "Internet") have been added. There have also been a couple of minor grammatical alterations and two spelling reforms. However, it is still basically the same language and I have no problem reading a text from that period (I'm a native German speaker).
Edit: If you're talking about the period starting with Germany's unification in 1871, that is. It is more difficult to read texts that were written before the 18th or 19th century. And it gets extremely difficult for any text written before the 1350s.