When learning these things (java, c#), you’re not really learning the language, you’re learning the frameworks. And there’s many of those, and each is bigger than the next. So you can learn one part of java, or you can learn one part of c# (eg, ASP.NET or WPF), and you still haven’t learned anything else.
You said you do SQL. C# has this really cool thing called LINQ. It’s SQL-like querries embedded in the language itself, which can target databases, XML files, even plain data structures. You might try learning this one part of C# and it’ll be very interesting for you and useful.