You can't learn C++ in just 15 days. You'll need at least a few months to get an ok understanding of the language. The tutorials here on this site may help you: http://www.cplusplus.com/doc/tutorial/
There's a tutorial in this very website. http://www.cplusplus.com/doc/tutorial/
You can learn the basics of C++ in few days if you already know something about programming.
If you want to learn programming and most of C++, you'll need much longer...
Learning C++ in 15 days is NOT impossible... It's just challenging! you just have to understand everything on your first try, be perfect, and have a great internet connection!
Well I guess it's possible depending on your definition of "learn." I was writing my own programs by myself after less than a day of working C++. Even though it took a while and it was a pretty advanced program, I got it done in less than a day. The program opened and said "Hello World!" to the user just like magic, I still have the program if you don't believe me.
I think to learn any programming language in anything less than a lifetime is being optimistic, but you can become proficient in C++ (somewhat) in 15 days but your going to need to devote yourself to it.
What takes longer to learn/hone (in my opinion) is the problem solving aspect of programming.
Syntax can be produced by looking it up in reference guides, what really challenging is solving a not so obvious problem, that's what takes the time.
The tutorials on this website, mention by Stupebrett & Bazzy would be a good place to start: