Answer part 1: This is practically impossible to answer for several reasons. First, the response could (and does) fill several volumes: one of the best examples of a comprehensive look at belief and custom is the Handwörterbuch des Deutschen Aberglaubens (Encyclopedia of the German Popular Superstitions), which appeared in nine volumes between 1927 and 1942. This is an exceptional work because it offers published material that most folklore archives only possess in unpublished form.

Second, you are asking about folklore from a historic period (presumably so the mods don't delete the question for lacking a period-specific nature?). Folklore can and does change, but the movement can be glacial particularly in pre-industrial settings. One can find evidence of folklore in written documents, but it is only by looking at collected material and then recognizing historical references that one can gather that the document is referring to something in popular belief/storytelling. No one was professionally collecting folklore before the nineteenth century, so this is the only means to surmise historical forms of oral tradition. In short, the only way we recognize folklore before the Peace of Westphalia is to consider folklore collected in nineteenth and twentieth centuries and use it to recognize and evaluate literary references before that time.

Third, Germany, as such, did not exist before 1870, and furthermore, German folklore is difficult to define even by 1871. The German inheritance was shared by neighbors. The traditions in the Germanies had a unique fingerprint, but the deviation from those of Denmark, France, and other European countries could be subtle and are at times only recognized by the specialist.

In a separate entry, I'll provide an example of how we can use historic manifestations of oral tradition.