With Google Earth open and your GPX file already imported -> Refer to this article if you would like to know how to download and import a GPX file.
First, we have to set the animation speed of the actual route travelled.
Select the settings "spanner" top left of the screen
Change the Animation speed to the desired one - below is a good example of what the speed could be set to
Save changes made to this screen and then move the time scale sliders all the way to the left side of the time bar
Click on the play button as indicated below:
The route travelled will start running from the start of day until the end of day.