For Back Office People Question

I'm learning the back office now. It's been a struggle for me to open fast on time. It's a lot of pressure for such a short amount of training time, and there's so much to do in a half hour. My question is, how long did it take you to get a good grasp and efficient at the back office? I guess I need a time frame of what to expect. I know it varies person to person. But no one at my store has given me a specific time frame for instance "Oh, it takes about a month" or something to that effect. I'm dreading on learning how to close. They said it's harder. Thanks for everything!