Need a help on range selectable react calendar.

[redsky500]

Hi, everyone!
I have some trouble in my coding while using react calendar.
Point is that range selectable calendar works well on wider resolution, but once the whole width get smaller like 400px, Its' style can't be changed. I want to second calendar down when total width is smaller than range calendar width.
In a word, this is responsible problem.
I hope author and other seniors help again.

PS. This is result what I want.