It seems that my income looks like it was doubled somehow. How can I delete and start over from the beginning?

You can clear your tax information entered so far, and start over in TurboTax Online, as long as you haven't paid yet, or registered in a free version - please see the following TurboTax FAQ, "How do I clear and start over?":

https://ttlc.intuit.com/replies/4248526