For what kind of projects is better use C/C++ instead Java or C#?

Answer 1

All of them unless C, virtually have the same capacities, With C you would deal with the low level stuff such as OS programming or micro controller programming, but there's no OOP concept has been covered by standard C.

Answer 2

C/C++ should be used when you want your program to have high performance. Java should never be used (maybe when you want portability). C# should be used when you want to work with .net framework (for example, developing games in Unity).