Lost language link after migration

Hi
I migrated posts from one site to another (using the Wp export).
In the original site I created the first post in italian and then I added (with “+”) the other 3 posts in EN-FR and DE lang: in this site I see the link between original post and the 3 other language on the upper right of each post.
On the new site where I migrated the posts, this link has been lost and so i still have each post with the right language BUT they are no more linked.
In same case the link is totally wrong or incomplete so the translation point to wrong post!
The consequence is that the site is no more correct.

Is there and easy way to relink original post with its relevant translation without rewriting all the site?
Thansk!