I've used way to many different languages to even count how many I 'know', but I would say I'm fluent in all languages based off of BCPL(which we joking refer to as 'Before C Programming Language'). C was created to replace BCPL because BCPL didn't have some of the byte-sized memory functionality that was needed for more modern Operating Systems, and also C introduced structs which IMO stream lined the use of object oriented programming most people use today. I also have used the languages based off of Algol-W, but they aren't as common as the language that branched off of BCPL(which is C, C++, C#, Java, and a dozen others).
The point of this paragraph is you shouldn't be 'learning a language'. Just understand the concepts and tools a language offers(like dynamic memory management using pointers in C++), and then use the API to branch out to other languages. If you know java, you inherently know C#. If you know C, you inherently know C++.