Some of my pages have both language in the same page

Hi,
it’s been a while that I’ve this problem, and I’ve always “solved” deleting the page and making a new one, but I’m searching for some other solution.
On my site sometimes a page show both english and right after the italian (and primary) version of the same article, right now I can see that when I look at the site in italian, how can I solve and separate the two pages (as it is when it work normally)?