Translation:We just arrived today.
"We have just arrived today" should be the actual solution. According to the British Council: https://learnenglish.britishcouncil.org/en/quick-grammar/just-yet-still-already
‘Just’ is usually used only with the present perfect tense and it means ‘a short time ago’.
I’ve just seen Susan coming out of the cinema. Mike’s just called. Can you ring him back please? Have you just taken my pen? Where has it gone? In the present perfect, ‘just’ comes between the auxiliary verb (‘have’) and the past participle.
I know that many American English speakers use the simple past tense with 'just' but the best answer should have the 'present perfect' as mentioned before.
One of the problems that occur throughout the course is that apprently the contributors are not familiar with perfect tenses and they are not accepted, even though in many sentences, such as this one, a perfect tense is the only grammatically correct option.
I an American, I would like to emphasize your point that the perfect tenses are rarely used this way in American English.
(I have never heard of anyone saying such a sentence without the 'have' though...lol) It is exactly 'today' which emphasises the time point at which we arrived, thus the perfect tense should be adopted. Grammatically, anything otherwise would barely make any sense (at least in BrE?)
There's no way of figuring out the meaning of the sentence based on the hints.
"We have just arrived today." I use the google Translate,but why here is said not correct.