and which religions did they follow?
Christianity, protestants, Muslims etc
German Empire
Catholic 
paragraph 231 of the versailles treaty dealt with It was the opening article of the reparations section of the Treaty of Versailles, which ended the First World War between the German Empire and the Allied and Associated Powers. who wrote it? Norman Davis and John Foster Dulles which countries were part of this empire? The empire  consisted of 26 states, most of them ruled by royal families. which languages did they speak? German, Polish, Danish, Dutch and Frisian etc
wiki:7774901
German Empire [SEP] Religion
Generally, religious demographics of the early modern period hardly changed. Still, there were almost entirely Catholic areas (Lower and Upper Bavaria, northern Westphalia, Upper Silesia, etc.) and almost entirely Protestant areas (Schleswig-Holstein, Pomerania, Saxony, etc.). Confessional prejudices, especially towards mixed marriages, were still common. Bit by bit, through internal migration, religious blending was more and more common. In eastern territories, confession was almost uniquely perceived to be connected to one's ethnicity and the equation "Protestant = German, Catholic = Polish" was held to be valid. In areas affected by immigration in the Ruhr area and Westphalia, as well as in some large cities, religious landscape changed substantially.