It looks like you're searching for a of a specific video file or download, likely an anime episode from the site GateAnime.
: The "b-nng" often refers to Black Clover in some file-naming conventions used by anime sites. gateanime-com-b-nng-51-bd-1080fhd-mp4
However, the term you provided——could refer to a few different things depending on which series it's actually from. Most likely, it corresponds to one of the following: It looks like you're searching for a of
: The "b-nng" is also a common abbreviation for this series. Most likely, it corresponds to one of the
Could you clarify you are interested in? Once I know the show, I can tell you if that specific episode is a fan favorite or if there are known issues with that particular release.
Because "Episode 51" is a major milestone in many long-running series, the quality or "usefulness" of the file (like the quality mentioned) depends on which show you are looking for.