C# used (by experienced devs ofc) as main stack when you do need to interact with windows eco-system itself (for example: mssql, domain system etc.).
C used as back-end only by masochists. Normal programmers use it only for complicated calculations, micro-services, as a transport layer etc.
Java using for enterprise.
JS mostly for real-time based sites or front-end (in 100% cases)
PHP for old big systems (FB, Badoo) or small-medium projects.