I spent 3 cashless weeks in Brazil last month. Didn't need to use cash, not even once.
Depending on where you go (specially the main cities in the South and South East) you can pay for everything with a credit / debit card, with very few exceptions - like the guys running around selling ice cream at the beach. Bahia and some places in the north you should be safe to use mostly card on daily shops (supermarkets, restaurants, events etc). Also if you're driving around, some highways will have tolls and they only accept cash, unless you are a local and have a green-go tag that gets the money from your bank or credit card.
Compared to Germany, I think Brazil is light years ahead in terms of card acceptance. To be honest I think Germany is one of the worst places to live if you want to go full digital.