Not able to hear songs properly in san...

Actually I am not getting properly what exactly I have to do according to this solution since I am not a person who has that much knowledge of re-assembling the player,

I am not familiar with this particular player, but this problem is usually caused by the headphone socket ground connection,

If the ground connection is lost then the right channel grounds through the left and vice versa.

If you can dismantle the player, check and re-solder the headphone connections. If this doesn't work solder a thin wire to a ground point on the PCB, then touch this to each connection of the socket in turn until the sound is restored. Solder the wire to this connection, and re-assemble the player.

WARNING : make sure that you have made the connection to ground. A live connection could damage the player.