a plane about how to learn German

Yes! Go to Germany and enroll in classes there, live with a German family, so you can speak and practice on a daily basis. If you follow my advice you'll be pretty good in 3 years.

Auf Wiedersehen!

If you are basing your advice on your personal experience, you might be leaving out the variable that you are German, and based on several factors can be educable beyond the average (person). It's my opinion, meant as a compliment.

Thanks for your advise.