Can one edit the sections in a Google form after sending it?

Yes you can.

First of all make a copy of your form(a test form), link it to a new answer sheet and submit couple of test replies.
Following that, make the changes you want and submit again some replies.

If you notice no changes to your answer sheet, continue by making the same changes to the original form. Problem solved 🙂

If you do notice differences to the answer sheet, then please follow these steps.

Important note
If I were you, I would first make a note -by checking the already existing timestamps- of when the least activity is registered and take the following steps during a passive period.

  1. Change the logic of your sections
  2. Unlink the answer sheet
  3. Relink your form to the same answer sheet.

Following the above steps a new tab will be created in your answer sheet where new submissions will be recorded.
To have results from both tabs together, create a third tab where by using formulas you can import date both previous tabs.