ò (r). The Russian 'r' is trilled. That is, the tip of the tongue is raised firmly to the top of the mouth and just enough air pressure is applied to cause the tongue to flap back and forth two or three times. It is is the same sound kids make when they attempt to imitate the sound of a motorcycle or a machine gun.
X (kh). This sound is produced similar to the sound of the letter 'k' in English except that instead of stopping the flow of air from the throat altogether, the tongue mere closes the throat enough to cause friction. The difference is similar to the difference between the sound of 't' and 's', which are produced in the same region of the mouth. The difference between these two, too, is the difference between stopping the flow of air and merely restricting it so as to generate friction.