It depends how many seeders it has.

Seeders are people who have downloaded the file already and so you're downloading the "pieces" off of them. If there are a lot of seeders, and they all have a good connection = fast.

Obviously your own connection matters too, but there's is just as important.

Similarly, if it's a rareish file, old, or hasn't been downloaded much - then the people who have in the past downloaded the file - may not be online or their connection may be busy for you to download from. Given that more may come online, or their connection speeds up - you'll get a better time.