Hellow again!
1. I dont really understand how to make a glass in JK2radiant.
2. How to make water?
3. How to make the sky or space.
I think that is all. Still i couldnt launch my last map couse of this error. Could it be to many textures?

1- You select a glass shader from the "common" folder under the texture menu. The texture should look like grey glass. Apply that to a brush.

2- Find a water shader and apply it to a brush. There are many, so do trial and error. (or make your own water shader with Notepad).

3- Go to the "sky" folder under the texture menu. Lookfor small white blocks with the word "sky" on them. These are what you use. The name of these small white shader should give you a hint to what they might look like. Then put these shaders on brushes. DON'T use the sky pictures.