I keep switching back to medic whenever a round gets messy. Engineer is the class I want to learn, but I spend half the map wondering whether I should be building, planting, or just staying alive. What helped it click for you?

Pick one objective for the round. My first useful evening was just keeping the tank moving. I stopped trying to be everywhere and started noticing where the team actually needed me.

Ask for someone to cover the approach before you pull the pliers out. I used to arrive alone, die, and blame my aim. The missing piece was usually another player watching the doorway.

The one-objective idea sounds manageable. Next time I will stick with the tank and stop changing class after every bad spawn.