Three Columns With Header

Banging my head against the wall with this one. Tried a few different tutorials. Basically, I just want the data on this page to be in three columns with a header at the top of each of each column (this would make the columns unequal lengths).

Here’s the website:
https://www.musicfestivaljunkies.com/festivals-a-z/

Here’s my scratched together code:
https://pastebin.com/EebcegKj