He has beans in his ears.
More German Proverbs:
Envy envies itself.German
There are no bad beers; some kinds are better than others.
German
Drunk sweetly, paid sourly.
German
A sparrow in the hand is better than a pigeon on the roof.
German
Liberty is God's gift, liberties the devil's.
German
Nothing should be done in haste but gripping a flea.
German