i want the pdf
Here are a few things you can try
Thoroughly look into what is implemented in c++ stl.
Implement all the algorithms you've learnt in as many ways as possible.
As you said implementation is your main problem, you might be messing up with the corner cases. Be careful with them.
Try to solve codeforces contest archives. Spend some time on each of them and then look into the editorials. This will help a lot if you plan to take ACM ICPC.