A video would be a really good idea, and I'd also recommend a trial that doesn't require a sign-up: if this were in any of the languages I'm constantly trying to pick up and it had a way of engaging me immediately without a sign-up I would have spent at least 20 minutes on the trial - I went down the site and did the english tests and it wasn't clear whether I got all the answers right! So, I would put a really clear call-to-action above the fold that takes you through a basic test and asks you to login/sign up on each step to save your progress.

I liked the format and variety of the questions: if you do well with this consider making french/spanish/portuguese/chinese/japanese/russian versions please!