Lets see:
For example you are a 10th grader and you really love maths and physics but the slow learning process is getting frustrating and you are taking a maths and physics course to become space ship engineer. But hey you already know the basics of maths and physics. So can you just skip to making space ships?
Well the same thing goes for making games.
Do you know the following in C++ and/or Java?:
Variables
Constants
Flow control
Loops
Functions
Memory management (Pointers and Stuff)
Structures
Classes & OOP
Recursion
Inheritance
Enums
Templates
Marcos
If so, go ahead. Else I strongly recommend learning more C++ and Java. But if you don't know those but you still want to go ahead, go and mess yourself up ;). I also highly recommend making some GUI and game engines by yourself using OpenGL, SDL or SFML, etc before proceeding.
And if you want to make games for Oculus rift with Unreal engine, you'd probably need to know more than just the basics.
Take as long as you need to learn C++. If you know all the syntax it will make it significantly easier for you to use whatever C++ engine you want to use.
A good website for learning is cplusplus.com, that's what i am using to learn. Or if you would rather have a PDF version tutorial a good google search will find the best one for you. In the past i have looked at YouTube videos and it didn't help me learn at all. It may be different for you but i learn better from an older professional than the kids on YouTube that i have found with my luck.