This is the 333rd most frequent Bulgarian word.
напълно
Completely; fully.
The word "напълно" is used here as an adverb to emphasize the total extent of being surprised.
Той беше напълно изненадан от новината.
He was completely surprised by the news.
Here, "напълно" modifies the adjective "завършен" to indicate that the completion is thorough and entire.
Проектът е напълно завършен.
The project is fully completed.
In this sentence, "напълно" describes the level of understanding, showing it as total or complete.