Old German handwritings
Old German handwritings can be collectively designated as running hand. Running hand is a handwritten script in which the letters are stanted towards the right and interconnected. There are many different variants and bastardisation of so called German script. Sütterlin is probably one of the most famous.
What is Sütterlin?
More properly the question should be "who is Sütterlin?" because Ludwig Sütterlin was the "inventor" of the writing and printing we today call "Sütterlin". This quite common designation is somewhat misleading, what we call "Sütterlin" was only the standardization of several different kinds of "German" handwriting, which became a common standard in Germany in the 1920s and 1930s. Sütterlin, a graphic artist by the way, did not create a completely new handwriting, but only collected the individual characteristics of handwritings in the 17th - 19th centuries. This meant above all an insistence on German cultural individuality with respect to its European neighbors, which explains its position as a mandatory part of the school curriculum in the 1930s.
The invention of the Sütterlin way of handwriting happened, as mentioned above, in more recent times. Especially legal files, documents, excerpts from church records, letters, diaries and private notes contain this type of writing which is difficult to decipher for modern day readers.
Along with this development many different spellings and dialects depending on which region of Germany the writer came from found their way into the written language. Only good knowledge of technical terms, regional characteristics, the historical context and enough practise make it possible to approach the true content of these works.