归功 is a verb-object compound (离合词) meaning 'to attribute (a success or achievement) to someone'. It is most commonly used in the pattern 归功于 (guī gōng yú) — 'to owe to, to give credit to'. As a separable verb, you can insert aspect markers or measure words between 归 and 功, e.g., 归了功 (guī le gōng) 'gave credit'. The object of the attribution is introduced by 于 or by a prepositional phrase like 把…归功于.