Quick answer:
If you’re male, you need to say Obrigado.
If you are female, you say Obrigada.

To reply back “you’re welcome”, you just need to say De nada.

But how do you say “thank you very much”? What is the verb for “to thank” or “to be thankful”? How do you express your gratitude in writing or when talking with people you respect? How do you thank people you don’t know?