You can reorder the questions or question groups by opening the survey builder. Go to the tab Build. Under Questions, you can see all the questions and question groups in the survey.
You can move questions and question groups by clicking -icon on the question, which want to be moved. Hold the click and drag the object to the wanted location.
Notice that you can move questions from different question groups by dragging & dropping the question to the desired question group. In the same way, you can move a question from a question group to be as an individual question without a group.
Learn more about building your survey here.