English of this period can be quite difficult to understand at first, but remember that one reason for Shakespeare's popularity is that much of his language is actually very bold and clear. For instance, Macbeth famously says that there is sufficient blood on his hands to make the "green" of the ocean "red." Later, he uses the same metaphor, remarking that he must "wade" through an ocean of blood.
The trouble with Macbeth is that, as a psychological drama, the characters in the play (accidentally or on purpose) do not see things so clearly: This play is full of shadows, foreshadowings, and shadowy meanings. So Shakespeare has to inform his audience, while allowing the characters to remain mystified, or "in the dark." This is one reason why the play is full of questions, most famously "Is this a dagger?" The answer, for both Macbeth and the audience, is unclear.
