So, I've told you I need an orthography source, but what do I want to know exactly? Below is the list.
Letter-sound and sound-letter correspondence: Basically, I want to know which sounds each letter has and when to use each letter to represent a sound. For example, for a letter-sound correspondence I can mention that 《l》 seems to be mute at times (such as in "selbst") but pronounced as [l] in others. For a sound-letter correspondence I can mention the letter pairs z/c and v/f, which can be realized with the same sound, [ts] and [f] respectively but are used instead of the other in very specific word positions or even types of words.
Diacritic usage: It refers to the quality each diacritic (comma, hifen, two dots...) have and when each should be used.
Other miscellaneous information about the orthography of the language, such as when to use capital and non-capital letters, the story of the german orthography encompassing its various standardizations up to the reform currently in use etc.
That's it! I've consulted wikipedia, a couple blogs and a number of English-written German grammars but the content in all were given only shallowly, thus not informing me as much as I'd like. The language of the source can be any from these: German, English, Italian, Portuguese. I don't know nothing of German at the moment but to just know the perfect source - even if it is written in german, would be a great thing in itself.