https://digital.diplo.de/navigator/en/visa
If you say you don't want to stay for longer than 90 days, it will tell you that you need a short-stay visa, but as a Brazilian citizen you are of course exempted from that requirement.
If you say that you do want to stay longer than 90 days and that you are a national of Brazil, you get this:
For nationals of Andorra, Brazil, El Salvador, Honduras, Monaco and San Marino
You do not need a visa to enter Germany if you want to study in Germany but you will have to apply for a residence permit at the local German foreigners office if you want to stay for more than 90 days. You do need a visa before coming to Germany to work or to research, as a job seeker or for self-employment. In this case, please chose “Any other country” as the answer to the question about your nationality to find out more about the right visa for you.
Now even a tourist does not need to arrive with a return ticket. You need to be a be able to prove, if asked, that you have sufficient means to leave the Schengen area at the end of your visit or other authorized stay.
Airlines rely on a database called TIMATIC that tracks entry requirements for countries all over the world. If I recall correctly it says "passengers who don't have a return ticket may be denied entry" or something like that. This is unfortunate, because passengers who have a return ticket can also be denied entry, for example if the officer suspects that they don't intend to use it. Similarly, passengers who lack a return ticket can be admitted if the officer believes that they'll buy a ticket home when they need to.
Update, I just checked the IATA Travel Centre, which takes its data from TIMATIC, and it said
Warning:
Visitors not holding return/onward tickets or sufficient funds to purchase a ticket, could be refused entry.
So even there it recognizes that the requirement is not to have a ticket per se but to have enough money to be able to leave.