Problems with tournaments

Hello, I apologize, I am french and I use google translation to write to you.
I downloaded the arcane theme. I’m just starting to do some testing to understand how it works to fit my clan. And I find myself with a problem with all the functions related to tournaments. I have imported the demo file but I try to access a page of pebbles (create, partake or other) I have a fatal php errors.
How can I correct this?