I think your issue, Panasanic, might be an overflow. I'm not 100% certain, but if you do have a lot of content in gmod and if enough particles are on one map, it might crash due to an overflow of usage.

This isn't a bug with just this map, but possibly for Garry's Mod. In every Episode 2 map that has the portal storm in the skybox, the portal beam isn't showing up. I'm not sure if it's only happening in my game or if other people are experiencing the bug as well, so I'm not sure if it works for you or not. If you know what's causing this or how to fix this, could you please let me know? Should I ask in the comments if anyone knows how to fix this?

I experienced the same issue at first, this should help:
http://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=132403761&searchtext=particle+fix

my error is that the beam does not have like the zapy effects like its rlly smooth looking

For me i do not hear the episode 1 ambience and i already have both episodes mounted to MOD and i hear growling which is creepy as hell lol