switch stick is the defense
Not claiming to be Henry or Skimbo... But...
1. Pick max 3 defensive shells (1 thats good against the pass, one good against the run and one thats flexible.
2. Learn 3 plays in each shell (one in man, one in zone and one blitz)
3. Whatever happens stick your shells and plays for 20-odd games and have a reason for calling each shell and play (down, distance, opponent's formation, time of game, etc)...
There are games where even the best players get dogwalked and other games where even noobs have a field day. I discovered that constantly changing my scheme/approach from drive to drive and game to game was counter-productive
You will get better when you do the same things over and over for a while (getting better at it)
The only thing u can do this year is find a consistent blitz,run a cover 3/4 shell out of it and practice looking at the entire field & switch sticking around to cover routes that look like theyre about to get open. There Is no correct answer to playing defense because zones are bad and man coverage gets smoked 70% of the time. Look at what type of route combos your opponent likes & set your zones to cover around those areas so u can switch stick on to them and cut the routes off. As far as the run game I don’t run the ball at all so all I can tell you is try to learn how to read defense pre snap, run that zone beater to one side of the field and a man beater to the other side and pray u guessed right