Yes it's possible and common to use multiple languages.
can you explain a little more. just an example how really it works?
for exmple how a python code uses output of a c# function. should it be a compiled library code or it can be simply done?
I find myself doing this all the time; hell, I am doing it as we speak. For example, I have an old piece of software that needed to target Android, PC, and iOS. Since I created the app on Android, the program was in Java. When I ported it to PC, I decided to stick with Java. When I ported it to iOS, I had to recode the app using Objective-C. The Android and PC version of the app shared almost the same code base, with the exception of a select few platform specific parts. The iOS version used the same ideals as the other two platforms, but was a completely new code base.
EDIT: I just looked over your last post again, and I believe you are confusing the use of multiple languages. What you are referring to "FFI." The language has to support calling functions from other languages; for example, C# offers the ability to call native functions from managed code. For example, with C# calling C++, the C++ code has to be coded in a specific way and compiled using CLR. You then hook the DLL in C# and bind your routines.
Here is some more information.