Stalker: Call of Pripyat → Quests → Dark Business
To begin this quest, you need to ask the Sultan for help with the Beard. He'll offer to ruin the bartender's business, or rather, take over his business, in exchange for a share of the profits and get your money back.
If you agree to the terms, the Sultan will give you your first task: find out what artifacts Beard is currently interested in. Talk to the bartender and learn he needs the Compass. Tell the Sultan about this, and he'll tell you to intercept the artifact.
Now go to Noah and ask for the Compass. He'll give it to you for free, but he'll quickly chase you off his barge. Bring the artifact to the Sultan. He'll learn that Beard has given his men upgraded detectors to help them find more valuable and rare artifacts. You need to start working for Beard to find the location of his stalkers—you need to take the detectors from them. First, we learn about Sledgehammer and his squad (most often found near the "Claw" anomaly).
We encounter stalkers, kill them all, search Sledgehammer's body, and retrieve the first detector. Now we search for Grebny and his squad (most often found near the "Sosnodub" anomaly), also killing them all.
We retrieve the second detector, report the successful heist to the Sultan, and ask if he's dealt with the rest of Boroda's suppliers. He confirms the supply lines have been cut off and asks us to convey his regards to Boroda. We approach the bartender and offer to work for the Sultan. He, realizing he has no choice, agrees.
As a reward, the player gains the opportunity to receive a percentage of Boroda's earnings daily. The player also earns the "Authority" achievement and the "Svarog" detector prototype. The percentage from Boroda usually ranges between 1000-2000 RU, sometimes less, sometimes more.
Source: ru.stalker.wikia.com
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