Fact is German does indeed contain many aspects of grammar that are redundant or less important. Giving each aspect equal focus seems as it were a methodological mistake. One field of German grammar has very high priority though: case. It is so important because it is a prerequisite in order to understand all the other structures of German. And this is exactly where many other courses don't lay the foundation that the student actually needs, but then how should he or she know about its value?
many people believe that to learn a language you just have to learn certain standard phrases and be done. If that's what you wish, I respect that. But if you want to really master German, you have to focus on grammar. After all grammar is not a set of boring rules. It is in fact the foundation and the secret plan of language, any language. You will see that grammar is not an abstract system, but can help you understand better.
What is language? Language is systematization of words. Mainly words consist of nouns and verbs, nouns are the most important category. The reason is simple. When you think of a noun, you automatically imagine an action that might be happening to it. Try to think of a person that you know. In your thoughts, what is he or she doing? There is always an action, isn't it so? When you refer to objects (things) you will find that they have a context because nothing on this planet is isolated and detached, absolute, one might also say. Take the context as the verb, the "action". Whereas you cannot imagine an action taking place without the noun that performs the action. Action is therefore dependent on the noun and not vice versa. If you want to be exact, the noun and the verb form a single unit. But for grammatical or analytical purposes we have to keep noun and verb apart.
So the noun stands out as one of the first constituent components of a sentence. In order to facilitate refering grammar we ought to define how we are going to use the term noun. See the German definition here.
You can understand the significance of nouns by regarding them as objects or rather as metaphors pertaining to objects which you have to imagine without motion, time and space. Motion and time are are outlined by verbs (tense). Usually objects "engage" in some kind of "activity". They fly, swim or simply lie somewhere. In fact they have an impact on the surroundings. The computer doesn't know it's standing on my table. We human beings create meaning. But must we emphasize its standing? I can also look at the computer in isolation, as if it were cut out of the picture. This is what we call abstraction. Abstraction is something you can increase. I can talk about my computer or about computers in general. Love is an abstract feeling. The word "feeling" is even more abstract, because it pertains to all feeling, like anger or sorrow. Our thoughts are always an abstraction, as there exists nothing - as far as can be observed - independently, existing in separation of the other. Something isolated, singular, essential exists solely in our mind. This is how abstraction is a reduction of reality in terms of essential fragments. Everything is intertwined. There are actually no fragments, no essential quality. We human beings have the capability of thinking rationally, that is to reduce the world into pieces. The world is too complex for us to understand, though we still think we might. We know that the butterfly's wing can cause a tornado, we know there's the atom, and by now, we have found that on a lower plane there are even smaller particles. Perhaps in a speck of dust that we carelessly brush aside there are endless worlds and planes. Who knows? We human beings write dictionaries and we categorize the world, big, small, black, white, but that is so, because this separation is important to us not the universe. For children there are little picture books. Inside you find images of everthing which is important for children, emphasized through colourful contrast. The tree, the mother, the spoon, the dog, the cat, the apple, etc. This is something essentially human.
John is writing a letter. John is the one who is performing the action. The primary constituent being John, he is the carrier of the main information that we want to communicate. In English you can't exchange this order, or if you did, the sentence wouldn't make sense anymore. The letter is writing John. (?) But in German this is possible because there exists case to support the significance of word order:
John schreibt einen Brief.
Einen Brief schreibt John.
Both variants are correct German (and logical). The second sentence differs from the first in that it stresses the role of the letter in the statement. But usually (in all languages) the nominative noun, being the pith of a sentence, protrudes at the beginning of a sentence, and this, too, in German. The second German sentence is not wrong, only awkward, meaning that the speaker has a certain intention to convey by exchanging the usual order. The main constituent noun (the performer of the action) is called in German Nominativ. In English there exist only remnants of case with the pronouns, like he (Nominativ) and him (Akkusativ), she and her, we and us, they and them, I and me. The Akkusativ is a secondary constituent, it can be regarded as a context, too, but we shall elaborate on this later in more detail. Fact is that this constituent (the letter) doesn't do anything or perform an action. For now we will take a look at the most important case, the nominative case, which points to the existence of a noun. The nominative (John) is the vessel of the whole of significance of this utterance or information.
You don't have to learn this table (now), just take a look:
|Case||der Brief (the letter)|
|Case||ein Brief (a letter)|