In every div2 contest it takes me more than 30 min to solve problem A and avg 15 min for problem B and 30 min for problem C. Due to that I am not able to attempt problem D as well as problem B and C gets submitted very late and my rank reduces significantly. I tried to analyse why it is happening and I came to a conclusion that problems other than A are based on ds, algo and A is based on logic and has too many edge cases. So how can I improve on that? Means which tags problem should I practice for that.

I tried to give atcoder contest as suggested by E869120 in his blog, but the question in atcoder are not like A. Should I play more puzzle games to improve on that. Any suggestion would be helpful.

Please also suggest the tags for the question which I should practice.

I apologize for my bad english.

Thanks in advance