The helicopter needs to be a prop_static or prop_dynamic

There are the questions for now:
How to make custom player models with sounds?
How to make a skybox?
Can i make the ground floor and by copying it make first and second floors? If yes, how to?

1. I know you can but I don't know how, there was one tutorial around if I recall on how to do it. Kind of a hard process I wouldn't recommend it unless you already know how to character model/rig.
2. http://www.tophattwaffle.com/hammer-tutorial-30-3d-skybox/ that tutorial covers how to make a skybox
3. I'm not sure I understand the question completely. If you are asking if you can copy paste the floor of a building you certainly can just select everything then in the side view while holding the shift key down drag it.

Not 3D but 2D Skybox. Is there any videos about both at once?
And how to make the heli impassable?
How can i thank you when the work ends?

For 2D you just forget about the mini skybox part and worry only about putting the skybox brushes/geometry in your map.

Make sure the model is set to solid in it's parameters or you could just make invisble player clip brushes covering it.

No need to thank me I'm just happy to answer questions.

Compiling map suddenly ends without starting l4d2. It began when i placed tools/toolskybox texture to the walls and roof of the world. What can it be?

Can you post your compile log?

Where to find it?

I said not to run game without key pressing `n i see that compiling ends.
When i press the key logging window closes and nothing else. There is no L4D2 or HL2 related processes(but hammer, sdk, steam processes exist). But if you say where to find logs, I'll send them

Oh that just means it finished compiling, launch l4d2 and type "map nameofyourmaphere" and it should launch your map

when i did such, l4d2 launched the old version of the map, with passable heil `n without some guns.
Map related files:https://docs.google.com/file/d/0BwMEVFsz7TdBa29IQXN2aFh6SzQ/edit?usp=sharing

Alright you have a few problems with your map:

1. One of your skybox walls is a func_detail. You can't have func_details seal your map.

2. The helicopter model you've selected has no collision model so you will have to use either invisible brushes or player clips.

3. The map is way to open. I know big open maps are cool but this will cause you a lot of problems later on once you start adding more detail. To start with you really don't need your map that high no one is ever going to get up that high in your map.

When i want to carve a place for a window with a brush, hammer doesnt do it. Why?
How to make fire as in the first map of first l4d2 campaign?

First off never use the carve tool it will really mess up your brushwork. Use the clip tool instead.

Env_fire can be used to create fire. You will need an env_fog_controller for the smoke to be visible.

How to make env_fog_controller to make smoke be only in the building?