How do I straighten my artboard once this happened

Hit the Escape key or double click the Rotate View tool (under the Hand tool) or choos 0 from the Rotate View menu at the bottom of your window.

Im sure there is a better way, but press and hold Shift + Space bar, while holding click and drag the artboard back to 0.00

Try the View menu

Or the document info in the bottom left of the document window.