Do not learn this song or this table by heart unless you can't help yourself because you love this song. You NEVER have to consciously sit down and memorize stuff in this course. Things will enter your brain automatically if you stop trying to learn or memorize things. This song is only here because it is a masterpiece of Margareth's and extremely lovely to some learners' ears. You can easily move on after having listened to it once or twice.
Don't worry about the cases (Nominativ, Akkusativ, Dativ, Genitiv) at this point of the course. Those will be explained very soon. This table is also mainly for your reference. In order to speak proper German the preaching technique will benefit you greatly.
You can't wait to understand what a case is? Ok. Then jump forward to the future. But come back here afterwards or you will be caught in a time-loop. ;-) Just kidding. You can as well just stay on track here. It will all come step by step.