The speaker never directly praises Natascha to her face. Instead, he praises her to his friend , forcing the friend to see her value. This is classic “bro wingman” behavior, elevated to lyrical art.
However, the phrase itself carries a very distinct, authentic ring of German urban youth slang , mixed with a personal dedication. It translates loosely to: Adding “full” at the end (from English “full” used as German youth slang for “really/absolutely”) suggests emphasis, like “voll” in German but written in Denglish style. natascha du bist die beste alter full
So whether you are Natascha, “Alter,” or just a curious German learner: Du bist auch die beste – Alter full. The speaker never directly praises Natascha to her face