Yet according to TIOBE C# us up 0.3%
Seriously though who cares what the "trending" languages are, it's like comparing web frameworks, it'll change next week and a new one will be along next month.
C# is primarily used for desktop apps, you can use Xamarin for mobile and ASP for web, and .NET core for cross platform and Unity for games.
You can also use VB.NET, or C++ or Java, or Javascript in frameworks like Ionic or React Native for mobile, web etc.
You use what is right for the project and what you know, if C# suddenly went to the bottom of the list (unlikely) would I stop using it? Nope.
As Wuerstchenhund has said, these surveys are not worth much.