Hello @zaid !
The first_published_at and last_published_at attributes are meant to be internal fields that cannot be modified. They are not editable as they are internal fields that we expose for your convenience. You can use them as meta fields or you can ignore them if you need to edit them.
If you want to have an editable field you should add an extra date-time field (or two of them) that you can use as you like.