This was one of the easiest quests that I have ever done. Essentially, I took four different sprites, of a girl walking, and made them into four different costumes. Then I put a sprite block that says When the start button clicked, ‘forever wait 0.2 seconds, move to next costume, and change x by 5. This creates the allusion that the sprite is walking across the screen while she is truly just changing costumes. One of the strategies and tricks that I learned was to set X and Y everytime the start button is clicked.
Here is my animation: https://scratch.mit.edu/projects/187506028/#editor