I has been 6 months since I start to solve problems from any online judge (Codeforces was the first one by the way) but since then, I barely notice a difference in my problem solving skills from now and 6 months ago even I had solve +100 problem and every time I register in a contest (div 2 or 3), my rate always decreases by -90 or more, and even If I managed to solve a problem It would be an A only.

So what should I do to improve my self even more? or begin a professional problem-solver requires lot of years practising? I'll be very grateful If you recommeded a few solutions based on your experience ^^

Thanks in advance.