Is "sono già venuto qui prima" a correct/usual way to say that I have already been here before in Italian, similar to "sono già stato qui prima"? I ask because the corresponding former sentence in Portuguese (a similar language) is usual, but I'm not sure the same applies to Italian. DeepL Translator has translated it to the latter. There is also a similar Duolingo sentence in the Italian course, but unfortunately sometimes its content is not idiomatic, so I'd like the opinion of native speakers.
Both sono già venuto qui and sono già stato qui are normal, idiomatic sentences. The variants with prima, however, are less so: they sound like translations from English (which, if I understand correctly, they are).
More colloquial versions would be qui ci sono già stato/venuto or ci sono già stato/venuto, qui.
Yeah I agree the phrase in itself is grammatically correct but as a native speaker I wouldn't use the word prima at all. The most common expression in spoken language is "Sono già stato\a qui" using the verb stare instead of venire.
1Benvenuta su Italian.SE e grazie del tuo intervento!– Charo ♦Jun 10, 2020 at 13:26