Topic of an essay

I would like to ask u about what kind an essay should I write in Common App. Should I choose already existing topics or Should I create a theme? If create, what a theme?
Thanks for your attention.
P.S. Sorry for my English; I am just a foreigner.

Common App Questions for 2019:

https://www.princetonreview.com/college-advice/application-essay-topics

Most likely just choose already existing topics as it’s easier to search up samples and know what people generally write about.