What does he have to do to get divorced?
have the divorce judgment passed by the german court recognised in turkey

Is this expensive? Do you know approximate price?
istanbul bar set approximately USD 2,000 for such a case,
which is of course subject to negotiation between the client and the lawyer.

How long does this formality take?
three-six months approx.

And once the divorce is finalized, is there a waiting period to get married again?
no...

info@hamle.av.tr