You always start from the end and go backwards from there until you will arrive at point where you are now. Now you see all steps clearly and what it would take to achieve.
Learn basics of Game Dev and I don't know how to start
Unity, Unreal Engine
Unity
C# and JS-like syntax.
So answer to your question is C# and Unity, but only to get started. Of course you shouldn't be focused on using ready Game Engines only but also learn how it works and write basic engine yourself from scratch someday.
After that you will also need to get your hands dirty with UE4 which is using C++. I would say C++ is a general Game Dev language and most of industry is written on C++.
Finally, it is never about a language, but as I said - about a goal. Game Dev is extremely huge industry and there are just too many types of games. Always start from the goal and ask yourself same stupid questions going backwards again and again. Now when you have some basics of Game Dev, C#/C++ and Unity/UE which are required by every Game Dev studio recruiting junior engineers, you will start asking yourself:
If it is "RPG with some PVE", then you just Google "How to build AI in C++ or Unity or whatever" and Google all the time.
Also browse source code of open-source engines and projects on GitHub and learn from them.
Focus on basics, on principles, and on theory. Become Guru of both 2D and 3D graphics from scratch, building basic AIs, UIs, physics and all the related math.
Principles and laws never change. Engines, language, teams, projects change.
Requirements define action. Not vice versa.