Веб-программист full stack (PHP/Bitrix, JS/Angular)

The task: refining, correcting errors and developing CRM real estate agency.
The project is archaic, self-written, undocumented:-)
At the heart of the CMS Bitrix and frontend framework Forza, based on Angular and Bootstrap.

An example of a problem to be solved:
"1. The interface has a button that used to be a click-through PDF with a table - a list of apartments that is appropriate to the one on the screen (i.e. with the same filters). Now for some reason it does not work - an empty file with an error message is generated. We need to understand why and fix it.
2. After that, you need to make sure that this button is only active for employees at a level not lower than the head of the department."

Another example of the problem:
"To transfer the entire project to the modern version of PHP (now 5.5 used), including finding a way to identify (and fix) as many bugs that will occur (there is no separate tester in the team)."

Budget - 20-30 hours per month at the rate of 1000 p.h.