Here's the objectives in English at least:
Normal
- Collect 1000 loot
- Steal the painting
- Return to the sewers
Hard
- Collect 1,500 loot
- Steal the painting
- Find the snake ring
- Don't kill anyone
- Return to the sewers
Expert
- Collect 2,000 loot (200 in gems)
- Steal the painting
- Find the snake ring
- Don't kill anyone
- Return to the sewers