Question

"Why haven't you been here for such a long time?" said Natalya to Lomov.(Narration Change)

Answer 1

Natalya asked Lomov why hadn't he been there for such a long time?

Hope it helps..

Answer 2

Whiile the sentence is interrogative, said changes to asked.

when we notice the reporting verb is said, we have to convert the inside matter into past tense.

Also, the most important rule:-

The question asked in narration is always changed to assertive in indirect speech.

Also, the preposition here changes to there in narration change to past tense.
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Answer of the question:-

Natalya asked Lomov why he had not been there for such a long time.