You might try creating deadening panels using 1x3 wood frames with carpet remnants tacked to them, or other heavy textile items such as tapestries, runners, area rugs, and the like. When I sound-conditioned my studio, I found this to be quite effective. The compressed fiberglass panels are by far simpler to put up (once you have wrapped them in burlap), but apparently not available in your locale. The idea is to introduce a material that will scatter the sound waves so they won't reflect as coherent sound waves. Corners are most important to cover, since they send sound back in the same direction it came from. Also, the walls at either end need to be conditioned to avoid slap-back.
I’d rather be told the ugly truth than handed a pretty lie.