How to Effectively Practice CP + Problem Solving Guide - Codeforces
From Beginner to Problem Solver: How I Improved My Competitive Programming Thinking - Codeforces
How to come up with the solutions: techniques - Codeforces
Easy problem 20 - 30 minutes
Medium Problem 1 Hr
Hard Problem 2 hours
Only after i run out of this time i can take look at editorless.