I want to know the difference between C and C++ and C# languages.

C language has no class concept.C++ is the addition of the class concept to C language C.
The C-language syntax is ++, but it is said that the C-language is incremented. I think it was named C++ in the sense.
C# was originally developed by Microsoft, but we wanted to make C++ better. C++ is incremented to C++++, and +++++ is arranged vertically to C#.
Therefore, in terms of language syntax, C# is the most advanced.
However, C# has been developed as a language for .NET, so native C language,
You will use C++.

C is the oldest language and is now used primarily in the embedded/IoT field/driver creation.
There is no grammar such as class, and void is written in the arguments of the function without arguments (remains of old grammar).

C++ is used primarily in speed-sensitive environments, libraries, and game development.

C# is now a language adopted by Unity (mono framework), but
Otherwise, it is one of the .NET languages that is supposed to run on the .NET Framework on Windows.
Used to create a web system as an exe for Windows or ASP.NET on IIS on Windows Server.
(*There is a .NET Core ported to run ASP.NET on Linux, but
I haven't seen it in my business yet.)

The areas used are completely different, so I think you should choose from what you want to aim for at first.