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

Yes

The word "manter" is identical in meaning, grammar, and spelling in both Brazilian and European Portuguese. The only differences lie in pronunciation, specifically in the phonetic realization of the vowels and the way the stressed syllables are articulated.

Brazilian Portuguese Examples

1. Precisamos manter a calma durante a crise. (We need to keep calm during the crisis.)
2. Ele sempre tenta manter o foco no trabalho. (He always tries to keep focus on work.)
3. Você deve manter o seu quarto organizado. (You must keep your room organized.)
4. A empresa quer manter os preços baixos para os clientes. (The company wants to keep prices low for the customers.)
5. É importante manter o contato com a nossa família. (It is important to keep in touch with our family.)

European Portuguese Examples

1. É preciso manter a calma durante a crise. (It is necessary to maintain calm during the crisis.)
2. Ele tenta sempre manter o foco no trabalho. (He always tries to maintain focus on work.)
3. Deves manter o teu quarto organizado. (You should keep your room organized.)
4. A empresa pretende manter os preços baixos para os clientes. (The company intends to keep prices low for the customers.)
5. É importante manter o contacto com a nossa família. (It is important to maintain contact with our family.)