Why WordPress AJAX returns undefined however it works fine when I add static url instead of dynamic function?

Because you have:

universityData.root_url

But you localised:

'root-url' => get_site_url()

root_url != root-url

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)