the unreal engine uses c# for development i can use to develop my games its possible?
No, it uses C++.
Some members are considering writing some wrappers to enable C# dev, but don’t expect anything useful anytime soon.
If you know C# you can pick up C++ fairly easily. Check out the C++ courses on pluralsight.com
C# code that you can find in sources are builder scripts and they are used in code project building, engine it self as said above does not use C# (or rather .NET-based byte code)
Now there is mono for UE: http://mono-ue.github.io/