I've read that you need to finish the Witch Hunter mission via infiltration AND ask about Sigi Reuven's treasure to get a reward from Djikstra for the Brothers in Arms: Novigrad. The problem is, I can't do both. If I ask to free Dandelion right away, I don't get a chance to ask about the treasure. And Menge gets suspicious and calls the guards if I ask to free Dandelion after asking about the treasure.