We're both wrong, it's 38.646,02€

Go to https://www.nettolohn.de and enter 64000€, choose Berlin, keep the rest. That's not enough for a modest lifestyle for a family, proven by the fact that with such an income, you're already entitled for social benefits (Wohngeld) in an average German city of 200.000 inhabitants for a family of 4: https://www.wohngeld.org/einkommen/#Wohngeldtabellen_fuer_Mi...

This is the government telling you: you can come work full time for us, but you'll not be able to provide for your family, that's why you can stand in line with all those who don't work at all to claim your benefits.