I know it is a kind of broad question but any answer are appreciated.
C# and Java are the two languages you listed that are most similar.  Python has a very different syntax, and uses a slightly different programming model.  Both C# and Java are Object Oriented languages at their core, with increasing nods to Dynamic Typing.  Python began as a Dynamically Typed scripting language and has been picking up more and more Object Oriented features over the years.  
The C# class library (.NET Framework) is theoretically multi-platform, though it's heavily weighted towards the Windows platform, and any other OS compatibility is largely an afterthought.  The .NET framework currently has two "official" frameworks for building windowed applications (Windows Forms, and WPF) and  two "official" frameworks for building web applications (ASP.NET, and ASP.NET MVC).  Windows Forms is similar to Java Swing, but the other four frameworks are very different from much of what is found in the Java or Python worlds.  There are many language features in C# that are different or lacking in Java, such as Delegates.
The Java class library is pretty solidly multi-platform.  It's officially supported desktop and web frameworks (Swing and J2EE) are generally regarded as slow, and difficult to use.  However, there is a very lively open source community which has built several competing frameworks that are very powerful and versatile.  Java as a language is very slow to introduce new language features, though it is runtime-compatible with several other languages that run on the Java platform (Groovy, Jython, Scala, etc..).  Java is the language which has has the most run-time optimizations put into it, so an application written in Java is almost certainly going to be faster than an application written in C# or Python. 
Python is an interpreted language (in general), and is pretty solidly multi-platform.  Python has no "official" desktop or web frameworks, though desktop applications can be written using GTK or Qt support, both of which are multi-platform.  Django has become a de-facto standard for Python web development, and is regarded as a very powerful and expressive framework.  Python is at this point fully Object Oriented, and is notable for it's powerful tools for working with collections/arrays/lists.  As an interpreted language, Python will be significantly slower than either C# or Java.
How Similar are Java, C#, and Python?