If you can program, you can program in Delphi. It shares most common modern programming paradigms with languages like C#. If you can't quickly make the transition from C# to Delphi you need to invest some time learning general programming concepts.
If you're going to attempt to maintain a large system written in one language (any language, doesn't have to be Delphi) while refusing to understand the language the application is written in you are unlikely to be successful. Similarly, if you make a habit of posting about the crappy architecture of a system you've just been hired to support, and the technical incompetence of your manager, you're unlikely to hold onto any job for a long time. That's true even if the architecture is genuinely crappy and your manager is a genuine idiot.
Frankly, I can't understand how you got hired to maintain a large Delphi system without knowledge of Delphi, or why you chose to take the job when there must be many more jobs available that require C#