For state tax: it said I had an overpayment and did I want to add it to my 2018 taxes. I accidentally hit Yes and it took my state refund to $0. How do I undo that?

After you file

The specific navigation instructions depend on the state.

To add, edit, or delete a state overpayment of taxes, please review the following general instructions:

If you're using TurboTax Online, sign in to TurboTax and select Take me to my return.
On the left panel, select State.
Select Continue to the Status of your state returns screen.
Select Edit on the State.
Select Continue to the State Landing/Summary screen.
Select Edit on the Other Situations.
Select Start or Revisit on Overpayment of Taxes.