It depends on host offerings of bandwidth as to what speed you get. The magnet link test is a good sign. So that simply means you need to find some good hosts to download from. Keep in mind some of those may be dial up users, some if not many are probably partial file sharers so the speeds may fluctuate, some users though they may have good upload capacity may be sharing it amongst many people so what's left over is smallish.

Are you uploading also?

People come & go online & offline all the time. So sometimes it's wise to re-search the file & find fresh search results. One technique that often works is stopping the download, then reselecting it from the fresh search results.

Another possibility is you are connected to one or more dud ultrapeers (or simply not performing well.) They do exist. So one thing to try is closing LW & reconnecting 10 mins later. Check the connections window & make a note of the ip's. Next time you reconnect, make sure they are not the same.