is it possible to select all the walls with a type of texture on it.

for example:

a map has 2 types of walls

blue walls and red walls.

is it possible to select only the red walls like in 1 click or something?

Depends on what you want to do, if you want to replace the textures, there's a function, if you want to select them, I dunno.

yea replace the texture

If you click on find/replace there'll be a window poppin up.
There, click on the first box and then click on the texture of your wall (or type it manually)
afterwards, click on the second box and then click on the texture you want to use (in the texture window).