Age has nothing to do with learning how to program, I can't find the video but I saw a video of a 12 year old making the top app in IOS. As long as you are really dedicated and intrigued by programming, you will learn it.
There is no set in barrier time to finish a book/ tutorial on c++. It all depends on how fast you learn, how dedicated you are, and how much you read/watch. To be honest, you shouldn't cram a huge tutorial in one day, lets say someone has a 20 video series on c++ operations or something that you have no clue about. You shouldn't watch 10 of them in a row, cause sure at the end of each video, you might understand THAT video. But you will forget everything else besides a few things. It's better to read a chapter/video and soak it in by using it, for an example lets say you just learned about for loops. Implement a for loop in a program so how that you make 100% by yourself, this will help understand the lesson learned instead of saying, "I understand it, next." Bottom line of this paragraph is this
If you truly want to be a great programmer and make a living off of it, there is no amount of time you finish learning, you are always learning, if you love learning about programming and actually coding; why rush learning it? soak it in.