Error 500 after trying to update and activate the contact form 7 plugin

Hello,

I work on an already existing website on wordpress, and I wanted to install the extension “Conditionnal fields” of the contact form 7 plugin.
However, after installing the extension, it has problems to work correctly.

So what I wanted to do was just to update contact form 7 from 4.1.1 to 5.0.5 (the last one), but when I try to do it manually (wordpress don’t propose the update automatically, I also don’t know why), I got a 500 error.

I tried to activate the debug mode in the wp-config.php file. Here is the debug.log file content : https://file.io/z3AGHG.

I saw that the php version used was 5.6.5, I don’t know if it is part of the problem.

Thank you in advance for the help,
Dan