looking for someone who can create material.cs files

Material.cs files are easy to make.
Just open one of them from any of the official objects and copy paste a section into your very own material.cs file and adjust it to match your object's textures.

Collision are done simply from the editor. You have to select 'Visible Mesh' if you haven't modelled a lower-poly collision mesh (Or select 'Collision Mesh' if you have).

 

Depends.
I will take it for granted you have a minimum of knowledge of 3D Modelling/Materials stuff.

Code:

singleton Material(barriere)
{
mapTo = "barriere";
diffuseColor[0] = "0.996078 0.996078 0.996078 1";
specular[0] = "0.5 0.5 0.5 1";
specularPower[0] = "50";
translucentBlendOp = "None";
diffuseMap[0] = "levels/GhostTown/art/shapes/barriere/textureforbarriere.png";
};

The part is red need to match the object's material name. I don't know if that's correct since I can't check your model. But you can check that yourself.

The rest is very simple. There are plenty of options you are not using in your material, so it may happear differently from what you wanted.
A good way to mess with materials is to have the really basic material working (Like the code you posted), and then edit it further using the 'material editor' in which you can find all the options and fine tune values. Just remember that whenever you save a material with the 'material editor', the material.cs file will be saved in 'Documents/BeamNG.Drive/levels/yourmapname/etcetc'.
In your case it would be saved in 'Documents/BeamNG.Drive/levels/GhostTown/art/shapes/barriere/


EDIT - If you don't have any minimum idea on how materials work generally, you should document yourself. You can try to run without knowing how to walk, etc.