Permissions don't work Its possible fix?

Hello I have a problem with the 775 permissions do not work whenever I apply them they do not work, I can use any type of permissions but no type of permissions is saved and I need 775 to be able to generate thumbnails. Upload an image. Permissions do not allow me to write.

Hello if I understand that but I cannot change the permissions they are always in 000 then that is an error of mine I suppose good thanks anyway