Sound design is dialogue, atmospheres, effects, and the mix. On set, location sound (boom and lavs) is the first defence. In post, a sound designer cleans dialogue, adds worlds, and balances music. Music producers and voice-over artists are related but different searches.
Bad sound is why Nepal videos feel cheap even when the camera is expensive. Budget a recordist or a sound designer, and rent microphones and recorders if the crew does not own them. Search sound designer Nepal or audio equipment rental on CineGrid.