Pentagon

You should really consider using a custom texture, like Fingolfin.

You are right but I dont really know how to use photoshop.

@purparisien Create a 512x512 empty drawing (You can use paint dot net or Photoshop, paint dot net is easier for me) and paste all the custom textures you need into the 512x512 drawing, you can put all elements/materials to it (like the cement floors, roofs, windows, brick walls) in the same drawing, now save the drawing in a .tga format and convert it to .blp with blpconverter, now attach the converted .blp to your model and re-UV-wrap the model.