You have 3 ways to move a question up and down.
1. Put your mouse on the question you want to move. See those floating buttons appeared on the top right corner of this quesition? Click on [Move up] or [Move down] button to move it.
This method is suitable for small adjustment.
2. Drag the question and move it to where it should be. This method is suitable for moving questions up and down in a single page.
3. If you need to make big changes to the whole survey structure, or need to move a question from one page to another, you will need to use the tree-form panel on the left side of Edit page.
Find the question you want to move in the tree form panel, click on it and drag it to move up or down.