Fast food can be rough.
If you want to be popular with your managers:
-CLEAN. OMG clean. "If you got time to lean, you got time to clean." Staying busy makes your managers love you. Clean off counter tops, restock vegetables, buns, cups, trays, sweep the crap off the floor, take the trash out. Wipe down tables in the dining room. If you don't do it, eventually, your manager will ask you to drop everything and do it anyways. So just beat them to the punch.
-Be prepared for the "rush." Business in Fast Food comes in waves. Breakfast, Lunch, Dinner, and at any time in-between. You need to be ready to shift gears when the rush hits, because it can be from 5 customer at once to 30 customers at once.
-Don't complain. Fast food sucks, everyone knows it. But complaining makes you unpopular, and you should be grateful to be working at all. Remember, some of the people you're going to be working with are career fast food workers, and they'll be older than you. Don't shit on their lives by shitting on the job.
-Keep your cool. This goes for any job, but Fast Food can go from boring to "ridiculously fucking busy" at the drop of a hat. So keep a level head when you're starting to fall behind.
-Will you be working the cash register? Be polite. If someone is being rude, let your manager deal with it, don't try to handle them yourselves.
-Will you be working the window? Be polite. Keep track of your orders and politely remind the people in the grill that they're missing your order. Because chances are, when that happens, they're in the weeds and are getting flustered themselves. Don't make it worse by being like "Where's my fries? Jeeeezzzzz."
-Volunteer to close if you can. This is optional, but offering to be a closer will make your managers love you, and will allow you to get to know them a little better. The bond between manager and worker is way stronger at night than in the day, IMO.