prepare for impact
Ok, this is going to be a long one.... get a tea, go to the toilet, call your friends and tell them you won´t be available for some weeks
ok, let´s start
1.you need to seperate your map in several boxes (blue=sky)
now, you have one big box and thats part of the reason it takes ages to compile
shift the bridgepart a little bit off, so it´s not visible from the other sections, build world geometry structures that break visibility between the different sections
2.i´m not sure, but i had nodraw walls in cashworks, still i could see opjects on the other side of it (mat_wireframe 1), i prefer using skybox-texture just for sure
3. Avoid diagonal worldbrushes, they completely mess up your visleafs, func_detail those
func_detail everything that is not main geometry
look at decompiled valvemaps to see how simple the underlying main geometry is without func_detail
4. viewdistance, viewdistance, viewdistance, make sure every object has that parameter calibrated. when it is on 0 it will be seen from everywhere
5. make sure every displacement outside the playfield is the _nodetail version of the blendgroundtograss texture. the decals might have only a small viewdistance, still it costs fps
6. Aesthetically, this rock makes no sense on the middle of a bridge, why should it be there in the first place?
7. i´m not sure about if this kills fps, but your water is unneccessarily deep, make it just as deep as necessary
8. Fog, your fogdistance is 11000, cashworks is like 4000,
the lower the distance, the earlier you can cut the viewdistance of an object
for the sake of gameplay and fps, cut the length of you long distances
i think from cp3 to cp4 on cashworks is the longest distance you can go with still tolerable fps. believe me, anything longer becomes bitchy
9. viewdistance traintracks
don´t ignore those, they need to be rendered and cost fps
by default their viewdistance is 1800-2000 and thats fine. in your map, the are always there
......
zat´s it
so, imho, first you need to rework the layout a bit and cut it down in skybox-chunks, then func_detail everything that is not main geometry, work with areaportals for all main geometry buildings, then adjust viewdistance etc.
a map of this size shouldn´t take more than 2 hours to compile with your rig
hope that helps