Counting the Omer

After all, after that I counted out loud the wrong number and the day has already passed. For example, in the evening I counted 13, then during the day I thought I was confused and counted 14, and then the evening of the 14th came. Should I count with a blessing even though I was of the wrong opinion, or because it is wrong, I continue counting, as I did, even though it was not in my mind at the beginning of the fourteenth day?

I don't think a mistake in the day spoils a correct count at night. It should be remembered that in any case what is not counted if a day is missed is itself a dispute over the first.
Although it is worth discussing the case that you also thought it was 14 in the evening but you got confused and mistakenly counted 13 (a double mistake). Here, in my opinion, you really missed the day.