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

Yes

The word "mensagens" is identical in spelling, meaning, and grammar in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. In Brazilian Portuguese, the vowels tend to be more open and the unstressed syllables are clearly articulated. In Continental Portuguese, there is a much stronger "vowel reduction," where unstressed vowels (like the "e" in mensagens) are shortened or almost swallowed, making the word sound more closed or compressed.

Brazilian Portuguese Examples

1. Eu recebi muitas mensagens hoje. (I received many messages today.)
2. Você viu as minhas mensagens no WhatsApp? (Did you see my messages on WhatsApp?)
3. Ele nunca responde às minhas mensagens. (He never responds to my messages.)
4. Eu apaguei as mensagens para liberar espaço no celular. (I deleted the messages to free up space on my cell phone.)
5. As mensagens de texto chegaram agora. (The text messages arrived just now.)

Continental Portuguese Examples

1. Eu recebi muitas mensagens hoje. (I received many messages today.)
2. Viste as minhas mensagens no WhatsApp? (Did you see my messages on WhatsApp?)
3. Ele nunca responde às minhas mensagens. (He never responds to my messages.)
4. Eu apaguei as mensagens para libertar espaço no telemóvel. (I deleted the messages to free up space on my mobile phone.)
5. As mensagens de texto chegaram agora. (The text messages arrived just now.)