Earlier quoted context omitted.
I don't understand one thing. Why Germany didn't interfere extradiction? (I assume that he held Germany citizenship)
Because Schmitz was in New Zealand at the time. Not much Germany can do to overturn NZ law. Germany is not the US after all…
There are things you can do, see how Russia is handling these things when their VIPs are targeted for extradition.
Ordinary citizens with no high up political or IC connections never receive any significant state aid in extradition cases no matter what passport they hold. At best your embassy might refer you to a lawyer or help you arrange money transfer from your home country.