Today you’ll be playing common spots in a tournament where you open in the Cutoff seat and defend against a Button 3-Bet. When a player to your left 3-bets regularly, you must defend against this by calling with a reasonable portion of your range and play postflop.
Keep in mind that turn and river cards can change the relative value of your hand within your range. Typically, when you are in the upper part of your range on a given street, you should continue with your hand. Static hands like 2nd pair can often drop significantly in your range when cards come that allow you to have much stronger hands.