With torrents no easy answer. I'd suggest patience is due. Some, especially older torrents may have those with the entire file on once in a while ... not too often. In meantime, some with parts of the file will log on hoping to complete the download.

Really does depend on download. Sometimes you may need to wait a week or two before someone with a part of the file shows up. If after a very long time you find not enough have the entire file, the search for torrents elsewhere.