Will someone ever get fired in a movie film if they keep forgetting their lines or emotions?
Yes, theoretically you could get fired, but movies are not theater. You get many takes and everyone forgets their lines once in a while (actually, these takes are often turned into bloopers at the end of movies). If you have problems memorizing lines, check out this page on the best way to learn your lines.
Being on a set for the first time can be nerve wrecking too and take you out of character, so don’t hesitate to ask for a moment from the director to get centered again if you feel you can’t access emotions. You’ll find that most crew members are very professional and understand the actor’s need to prepare and stay focus.