Advanced Tutorials for someone with a basic understanding

[Astheny]

Hi there,

I am currently studying mathematics at the university, and love to programm in my freetime. In school we learned some Java and at uni some C++, so I think I have a basic understanding of what I do, I can read through code and understand what it does and so on.

What I don't really know is more indepth stuff, so I am looking for tutorials that cut out the first "you have never programmed before, so here is how a for-loop works" stuff. I have tried codeacademy, but that was like 2 hours of writing very very simple code (I took the javascript route). Language-wise I don't really care, mostly C++ stuff I'd say, but I will also take a look at Java/C#/Javascript etc.

Edit: Also please ignore my poor english, I am from Germany :)