Patience is truly a virtue. There is a lot to learn and it will take time. You WILL make mistakes, hopefully small ones, and the objective is to learn from each and avoid repeating the ones you make. You'll receive a lot of advice, most of it helpful, likely some of it not. Follow the advice that works and disregard short cuts and cut corners (eventually they'll bite you).
The more "snaps" you see, everything you're looking at will slow down. You can NEVER see everything, so learn to focus on your assigned (by your position) areas and targets (keys). Be polite, respectful and attentive on your sideline. Follow the advice (from the movie "Roadhouse") and, "be nice, until it's time NOT to be nice", but even then be RESPECTFUL.
WHEN you have a "brain freeze" (you have a different down than the box, or some other "needs to be corrected" problem) STOP play from starting, go directly to your Referee, privately get things straight and go back to your position, NOBODY will KNOW what the problem might have been, and you'll avoid a possible mistake.
Understand, that no matter how long you may chase perfection. as hard as you can, the best you can do is get closer. Although you'll NEVER catch it, you'll really enjoy the chase.