Is possible to make the map/level outside UE4 for example on Autocad?
Yes, as long as you can export it as a fbx or heightmap (landscape) it should work
And it will have some impact on performance compared to BSP? Or it will have some diference between fbx and make inside of UE4?
Actually it will have a better performance ^^ -> bsp are just used to protoype your level + for basic stuff
I export my existent map to Autocad but my whole map is in one piece
That’s the main problem when you create your entire map in a 3d program -> normally you just create the meshes for the level in the 3d program and after that you create the level in the engine.
I dont know how you can import the file as separate meshes into autocad, but in the ue4 you have to disable “combine meshes” -> but this will just import the meshes and you will have to recreate the level in your 3d program. So either you re-create your level in the UE4 or use one single mesh for it -> I think that there are some scene exportes for the UE4 and 3ds max (just search for it on the internet)
There is a Trello card about the feature to important all of the static meshes from an FBX in their original position. You can vote it up here: Trello