After the 1st Question, just add another question “Which type of pizza”, you’ll use a filter for this question that the answer to the 1st question was ‘Yes’.
You can then add another question “Do you want another product?” and again using a filter, you can choose that the answer to the first question was ‘No’. (you are simply using outputs from the 1st question here)
You could also use a Label and go to Label actions - A label will let you jump to a certain point in your Flow so you can only carry out those actions so for instance after the 1st question, you could go to label ‘Back’
Hope this points you in the right direction
if you get stuck or need more help email us at firstname.lastname@example.org