Welcome to the community, @Clement_Deschamps! :grinning_face_with_big_eyes: There are a couple of ways to do this:
In your second form (which would be built in a separate table), add a link field that lets you link to entries from the first form. When sending the link to the second form, use Airtable’s form-prefilling feature to prefill that field with a link to the original user’s record (using the record ID). The problem with this method, though, is that the user is free to remove the link, plus they could also see all other users who filled out the original form if they tried to re-make the link again.
A slightly safer way is to insert the user’s record ID into a plain text field in the second form (also using the prefill feature), and include text in the field description that discourages the user from modifying that field’s prefilled contents. I say “slightly safer” only because the user can still delete the text if they want, but they can’t see other records this way. (Unfortunately Airtable doesn’t currently allow for fields to be hidden and also prefilled, or else this would be a non-issue.)
Edit: you could also use a third-party form tool like JotForm for the second form. JotForm does allow hidden fields to be prefilled, but there’s more work required to get the data from JotForm back into Airtable.