i solved temporarily this problem with "sudo mount -o remount,rw /" and copying my ringtones to "/usr/share/sounds/ubuntu/ringtones/" via "sudo cp myringtone.ogg ..."
he final solution, (i hope) will be the possibility to set individual ringtones in contacts. maybe in release 16.04.
i solved temporarily this problem with "sudo mount -o remount,rw /" and copying my ringtones to "/usr/share/ sounds/ ubuntu/ ringtones/ " via "sudo cp myringtone.ogg ..."
he final solution, (i hope) will be the possibility to set individual ringtones in contacts. maybe in release 16.04.