A friend of mine posted a couple of notes on her travel blog about getting stuck at GRU for a day, thanks to a Gol-Delta misconnect.
http://thewanderlife.com/stranded-in-sao-paulo/
Fortunately, she's Uruguayan so does not need a visa to exit the airport. I've been at GRU for nearly 24 hours on connections, at least it felt that way, and I could not, as a USA national without visa. Even with a Uruguay cédula, the 2007 revision to the Mercosur treaty bases entrance on nationality, not residency in the bloc.
Sadly, the last three times I was there on long connections, long after I lost any elite status with lounge access. Not that either the Smiles nor the United lounges were any great shakes. But they certainly beat hanging out in the gate areas. Functional but not fun airport.
Not sure if the OP needs a visa or not being from Germany, as I haven't looked into that scenario. But impossible to get one upon arrival in Brazil, so if you don't want the capsule hotel in the walkway between the two international tiers, you should verify before your trip.