Dumm ist der, der Dummes tut

Das ist der Original-Satz aus dem deutschen Film.

I don't think we say that at all.
Nor do English-speakers, for that matter. It's a variation of the much more sensible idiom: Handsome is as handsome does.
(Which we don't say in German, either, though.)

You could translate it as: "Dumm ist nur, wer dummes tut", I guess

I grew up with "pretty is as pretty does"