Is the word voltamos the same in Brazilian and European Portuguese?

Yes

The meaning, spelling, and grammatical function of "voltamos" (the first-person plural of the verb voltar) are identical in both Brazilian and Continental Portuguese. The only difference is in pronunciation. Brazilian Portuguese tends to be more "syllable-timed," meaning the vowels are articulated more clearly and openly. In contrast, Continental Portuguese is more "stress-timed," which causes unstressed vowels—such as the "a" in voltamos—to be reduced, clipped, or almost swallowed entirely.

Brazilian Portuguese Examples

1. Voltamos logo, não demora. (We'll be back soon, don't take long.)
2. Nós voltamos para casa agora. (We are going back home now.)
3. Voltamos a nos falar amanhã. (We will talk again tomorrow.)
4. Voltamos para o Brasil no mês que vem. (We are returning to Brazil next month.)
5. Eles não voltaram, mas nós voltamos. (They didn't return, but we did.)

Continental Portuguese Examples

1. Voltamos logo, não demores. (We'll be back soon, don't take long.)
2. Voltamos a casa agora. (We are going back home now.)
3. Voltamos a falar amanhã. (We will talk again tomorrow.)
4. Voltamos ao Brasil no próximo mês. (We are returning to Brazil next month.)
5. Eles não voltaram, mas nós voltamos. (They didn't return, but we did.)