How to learn enough C++ to program Arduino?
If I were you I'd take the high road.

I was in your shoes a while ago and I didn't know how to approach Arduino. I was very lucky that I came across a book written by the famous Jack Purdum, "Learn C programming for the Arduino". It is written by a retired Purdue University professor who is well known for his extremely easy to learn teaching method. He has another 

I only knew MATLAB and Simulink before starting this book. This book is amazing. It was extremely easy to follow. I now have no difficulty programming Arduino in the correct way. This book trains you to optimize everything which is very crucial with the limited resources on Arduino boards.

I suggest C instead of C++. It is the language of choice for programming embedded system. It is said to be low level, but as a MATLAB user I should tell you that syntaxes are extremely easy and intuitive. I didn't find anything hard about them.

Remember:


There isn't any problem to use C in Arduino IDE.
You don't need to worry about libraries. You only need to load them in the beginning of the code. You do not need to know how was the code written in the library.
Check the comments about the book on Amazon if you are not convinced.


Good Luck