So, I'm new to mapping, and when I tried to make a different terrain style in radiant (Simple Curves, Simple Terrain, Primitives, whatever) the texture just don't apply to the terrain/brush, I tryed everything, maybe I messed up some stuff, but sill only shows the outlines of the curves, instead of the outlines WITH THE TEXTURES. Could someone give me a tip of what's going on??? I'm following youtube tutorials by the way.

I dont have any idea but just try to select the patch and click ctrl + I because maybe is inverted(I don't think so). Anyway just create a new, patch, simple terrain patch, apply the texture, if it doesn't appear click ctrl + I. You should post any image btw, it's better, also maybe you have disabled any option in radiant  but I don't really know what to say for now. 

Radiant toolbar "show patches as wireframe"
There is also "j" , "shift + j" , "ctrl + j" to toggle the red highlight and textured wireframe modes when blending or vertex editing.