Understand the work of php scripts

You need a very experienced programmer.
I downloaded the script, I need to help figure out how it works, and why the clients site does not work on my domain.
consists of the clients website and admin panel
php stack 7.4
you need a middle-senior level to quickly understand what is why how it works, find the cause and help run.
as part of the complex there is an obfussed js file, it is necessary to understand in php kb its coding occurs. I already have a partially deobfused file, executed manually, but whether it will work is a question, I need help to understand this.
If for you the ethical issue is acute, then you will not like the subject))
Write in the telegram, explain the details and show.

Budget 150$ payment only upon completion.