"I sleep because I do not work today."
Translation:Śpię dlatego, że dziś nie pracuję.
It is an article from a Polish tabloid "Super Express". It says "I am not sleeping because I am holding the cupboard". On the top there is information that "Because of speeding lorries the house of Mr Andrzej is trembling". Actually, acording to this article, at the moment he does not hold the cupboard because it has fallen apart but still he does not sleep.
You made the mistake of treating the Present Continous construction very literally. Well, actually the default sentence here used Present Simple, but it could be Continous as well. Anyway:
"to be X-ing" (I am working, for example) is just a construction. There isn't any real "to be" there. The only verb that you should translate is "to work". So in a way you wrote "because I am I work today".