I want to create games with this engine. My question is: What programming language this engine uses? Is it C++ or what?
Is there any answer to help me?
Well the engine is written in c++ I believe so that is available and for a lot of things its mandatory for execution speed-- Many , programmers and new users, often use Blueprints and you can make an entire game WITh Blueprints .
This will get you started easily https://docs.unrealengine.com/en-US/…ing/index.html
On Fanatical there is an eBook bundle of 25 eBooks at a cheap price for Unreal Engine 4 programming which includes C++, BP, VR. You might want to check that too.