There are two basic questions that always apply, one of which I can answer for you and another only you can answer.
Is your site targeted?
Taking a look at your website, it doesn't appear targeted at all, which makes it very difficult to qualify traffic in the first place. By making it very broad, you end up hiding the few courses that I may be interested in among all the courses that I'm not interested in. If you were dealing with something more specific, like cooking, it is much more likely that someone interested in cooking would convert, and a high percentage of your content would interest them.
Your site seems to be a fairly eclectic mix of topics which do very little to add value to each other. You should consider narrowing your target down to a specific topic area. It is always easier to expand into new topic areas once you are doing well than it is to enter all of them at once.
Is your traffic qualified?
By qualified traffic, I mean traffic from a source that is relevant to your website. It's fairly easy to get general traffic to a website, but that traffic has almost no conversion.
Imagine two scenarios. In the first you get 1 million unique hits from advertising on a torrent site. In the second you get 100 thousand hits from links on a number of blogs dealing specifically with adult learning. Which do you think is more valuable? The second one of course, as they are far more likely to convert than the first.
If your site isn't targeted, it is going to be very difficult to get qualified traffic in the first place.