Hey Ting,
I’m sorry we can’t answer that without knowing what look you exactly want for phone screens. There are lots of possibilities and options to set.
The easiest way but not optimal is to add another Bar to be used for mobile display. After you built the bar, hide the bar on desktop / laptop view by using the Hide During Breakpoints feature. Similarly, hide the 1st bar on mobile views. You can learn about that feature here https://theme.co/docs/hide-or-show-content-by-device-size
What I’d recommend though is you learn how to use the Flex options available in the elements especially the Bar and Container so you can control the display. You can start learning here https://theme.co/docs/use-flex-layout
Hope that helps.