https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-1-submit-a-petition/step-2-begin-nvc-processing.html this link explains the steps

hi, how long take to aprproved you case ?

I submitted yesterday

3 months

wuaooo and the interview date do you got ?

still no interview yet they just approved and accepted all the documents I sent 3 months ago I wonder if I have to wait another 3 months for an interview

From another post here, it takes maximum of 90 for NVC to send your papers to US consulate which then will assign the interview date based on their schedules.

I submitted all documents and qualified 3 months ago waiting for interview letter nvc nothing yet