Dear Rebecca,
The Calendar you are using is based on http://intljusticemission.github.io/react-big-calendar/examples/index.html and does not support multiple events side by side in a column in a better way.
You could check the other calendar as well. https://appstore.home.mendix.com/link/app/248/
Cheers, Andries
The other calendar widget(as Andries states) is based on the fullcalendar library. This has an option to overlap or not overlap(by default it overlaps)
https://fullcalendar.io/docs/slotEventOverlap
You could edit the calendar.js to set the slotEventOverlap: false, (below the var options).