Six hours is along time to be stuck with a group of people. I think you did well to stay until the end of it.
Are there any more short classes?
Six hours is horribly long indeed.
Why didn't they cut it into a few shorter sessions?
I had a few shorter ones, were we did some practical exercises. And where we most of all learned to physically relax.
In the end, when you give birth, either your body does all the work it needs to do by instinct, with maybe a few helping suggestions from a midwife or doctor, or the medics will take over. People have gotten kids without a course for centuries, and if you have a doctor or midwife to rely on, you will do great, also without a course. Most important thing is not to worry too much I think. If need be, there will be a doctor taking over.
Hope it will be a great thing for you, giving birth.