Certainly in other languages like my native Swedish, a negative is expressed with the verb followed by not.
Jag pratar inte Svenska = I speak not Swedish = I do not speak Swedish
In English, however, a negative is expressed in a very odd way.
I do not speak Swedish.
The DO NOT seems to me, to be a double negative, and should cancel itself out to leave - I speak Swedish!
In older styles of English, certainly language around the time of Shakespeare, it was common to write: I speak not. I speak no. = I do not speak.
How did the verb in bold evolve to the I do not speak construction that we use today?