Are you making this common mistake when speaking Portuguese?
Learn what it is and how to fix it by watching this video.
It is very common for foreigners learning Portuguese to overuse the word sim when answering questions.
If someone asks you a question you should respond using the same verb that the question was asked with.
Foi ele que falou isso? Was it him that told you that?
Foi. Yes it was him.
Você gosta de pão de queijo? Do you like pão de queijo?
Gosto. Yes I like it.
Posso te ligar amanha? Can I call you tomorrow?
Pode. Yes you can.
It would be incorrect to reply to these above queries by simply saying sim. If you did this the Brazilian who asked would likely be confused and give you a strange look.