No, please do not add the amount of taxable Social Security benefits by hand (in Forms mode, I assume is what you meant). This invalidates the Tax Accuracy Calculation Guarantee and may block you from being able to e-file.
When you enter the lump sum amounts as described in this FAQ, you are not guaranteed that your taxes will go down, only that they might. It depends on your answers to the interview. Your answers between 2018 and 2019 will likely be different.
As you may know, the Free Edition of TurboTax does not provide phone support. If you have a question, you can ask it here on the Community with more details and we will try to help you.
If, however, you are using a paid version of TurboTax, please see this TurboTax FAQ for phone support.
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