What is the right way to say in English "Today it was the final exam"? (When I googled this sentence. I've got just 1 result. So I can guess that it's not correct. Am I right? (I'm not a native English speaker as you can understand)
I would say that the best option would be:
The final exam was today.
This would answer the question: "When was the final exam?". If the question was implied (that is, if you wanted to say that the exam was today without anyone asking you) you could use the sentence given above. If the question would preceed the answer (in a dialogue) it could go like this:
"When was the final exam?"
It was today.
Here you would use the personal pronoun it instead of the phrase the final exam, to avoid repetition. The final exam in the first example and it in the second one, function as a subject in a sentence. The sentence follows a classical word order pattern for English: subject + verb group. Here the verb group is: verb to be+ adverb (of time). Also note that to be is here used as a full verb (not as an auxiliary verb).
Another way to phrase your sentence can be:
Today was the final exam.
This could be an answer to a question: "What happened today?" Where the final exam would be moved to the end of the sentence to emphasise that this was the answer to the question.
Choosing between these two word-order arrangements is a matter of nuance in meaning and depends on the context. (For both sentences in spoken language emphasis would rely on intonation more than on word order. Even in written form what is emphasised can be interpreted differently depending on the context).
In conclusion, the sentence "Today it was the final exam" is not (commonly) used because it has two subjects "it" and "the final exam" or more precisely, one subject that appears twice.