Hello! I'm Dare, creator of the halloween map! A few fixes that could help would be the following-
• Delete the MyParticles.fho in your exports
• Make sure you have no particle duplicates!
• Switch your rendering system to Direct
• Turn off your water reflection
If none of these solutions work- It may mean there are too many people in the map for your computer to handle and that would be a computer issue rather than the map. Please update me if anything works!