Dear Barbara,
I am actually a software developer by profession. I know many languages, including C, C++ (C plus-plus) and Java, so learning a new one, especially one similar to those, isn't a big deal for me, skill-wise.
My issues are more of a personal/emotional kind than an intellectual kind. Yes, i do intend to try to do both... singing and C#. need to pay (my own) bills.
C was not really one of the first languages... hmmm... well, nowadays, with all that has come out, i suppose you could say it was, LOL! It's definitely an old staple by now. I learned it 20 odd years ago, right out of the original Kernighan and Ritchie book.
To try to answer your question, C# (C sharp) is a full blown object-oriented programming language, syntactically and conceptually similar to C++ and Java. You can develop any piece of software with it. It is not specifically for web content. Web applications designed in it would have to run on the back end (server, not the browser), where it would require the .NET framework which is MS Windows based. I think there may be some sort of emulator for Linux but not sure - something i need to find out.
HTML and CSS are not, strictly speaking, programming languages. They are made up of data formatting directives, not machine instructions, and they do not have the concept of flow control. Mind you, when i code in HTML, i sometimes call it "programming" too - so, sue me! right?

but it is technically more accurate to say coding - which is generic, or authoring.
hope that makes some sense. not sure if i have clarified things or made things more murky.

I hope you are able to get into this stuff more, once your eyes are fixed. It sounds like you have a real interest in it.
~ waves ~