Hey German Student
I had a lot of trouble with the AW section too, just cuz there is so much out there to help you with your quant, verbal but hardly anything on this section.
Magoosh is great. Are you referring only to the blog? Cuz if you sign up for the lessons, you have one set devoted to AW, which is great. That in combination with the Magoosh blog, where for example they divide the question pool into topics. Barron's book helps you to identify these topics as well.
But the most helpful thing I think is going painstakingly through all ETS solved examples. They have 2 for their practice tests on website and 2 in their official guide book (that I am aware of). They might have more. Really examine how the top scorers have answered. And before that, write out the answers yourself and then compare to see how you are falling short. It might not be immediately clear, but by the 3rd or 4th solved ex, one starts to see patterns.
Its also not enough to just answer the prompt not keeping the specific task instructions in mind. All top scores have that in common that the answers are framed using the word "argument/claim/recommendtaion" etc that are there in the task instructions. Notice how the 1st and last senetnce of every para is framed using the task instructions - ie each point is presented using the language of task instructions.
And I'd say Practice practice practice! at first untimed but then timed. also, for the issue task, try to go through all the prompts before test day, orally trying to figure out at least one point/example you can make for that prompt, so that you are not seeing it for the 1st time on test day. and if you are not able to think up any point at all for some essay, then google n try to read up somehting on that subject or on anything you think you might potentially use as an example.
All the very best!
PS: are you planning to use interfolio?