monika_.19: I think there are two issues here: one is about search indexing, and I think the duplicate key errors are another.
For search, you might need to reindex the entities. This requires setting yourself up as administrator, visiting the admin page, and indexing authors (for example, to test if everything is ok).
We don't yet have a handy script to set privileges so you'll need to modify the database and set the column 'privs' to 31 for your user id.
You'll now have admin provileges,  and you can visit `localhost:9099/search-admin` and click on the first button (person icon) to reindex authors.
Then once that is finished, try the autocomplete again.
If all is well, click the last button on the search admin page to reindex all entities. This will take a little while depending on your machine.