Trying to reduce polygons (decimate) is not an option https://cdn.discordapp.com/attachments/191625599176015873/415621667432300545/unknown.png This is my current model for a health charger in Garry's Mod however the poly count for it is Verts:833,385| Faces: 831,002| Tris:1,662832 its too big to import into the source engine with all those polys (I get a crowbar error). The reason why I cant use decimate is because the mesh screws up before getting a reasonable poly count
You'll probabably have to do retopology and then bake the normal information into the low poly one, in case you don't know what I'm talking just google "Bake in blender high poly to low poly" or something of the sort and you'll find plenty of tutorials on how to do it
Also you could always do this too: Youtube link