Many people will say that you can always focus on C++ as the majority of engines are written in C++ and you just get the source code license of the engine, use C++ and your good to go. While this might be mostly true the simple fact is many of us independent game developers simply can't afford the source code licenses of engines that we might want to use. These decisions can be made once your design document is done, you can compare what your trying to do to what various engines (and their different licenses) allow. Then you will have an idea of what programming languages you will be able to use to code your logic around that engine.
There are many free frameworks that are written in C++ that you can build your own in house engine around or you could always write your own engine (in which case I suggest nothing but C++). However if your goal is to make a game (maybe even to sell it) you don't really want to waste your productivity on reinventing the wheel so to speak. There are free licenses to engines that are already powerful enough to handle the majority of independent game titles already, doing all of that work yourself will consume years of time and greatly diminish your interests and motivation in completing the actual game (many times this causes the team's and their projects to fall apart and give up).
With all that mentioned please check out two of my journal articles for a little more information on both of these particular topics. The "Who Needs a design document" will explain in a bit more detail why that design document is so important and is the starting point for actual project development (which can also be a starting point for you learning the art of game development.) The second article "The Programming Primer" is a large detailed overview of what it means to program, some general terms to get started with and tries to make a connection that you as a beginner can use to start understanding that the language doesn't necessarily matter it's more so the art of solving problems. It's quite a bit of reading but might just help you get your bearings and get started with a bit of an idea what you are getting in to and how to go about it.