You are born an actor! Facts! So, why are you taking classes to learn how to act? You should be taking classes to learn how NOT to act!
Personally, I never memorize a script for film. I do not want to appear rehearsed and too polished to be realistic on camera. Instead, I learn the story and approach the process of acting much in the way we play the game of Gossip as kids: You hear the story, you know what happens to whom and who said what, and then you go elsewhere and repeat it, telling the story to the next person in the most believable manner as possible, even if you make up some of your own parts. I read the script to learn what happened to whom but that's as far as I take the script.
I will start by expressing that acting is acting, yet everything you do for stage, you must do just the contrary for film. On stage you can pretend something happens, but in front of the camera you should experience it happening. Instead of expressing outwardly for stage, you need to internalize for film and let your eyes and voice do the speaking. Rather than exaggerate, you need to simplify in order to be realistic. And rather than knowing every single line by heart and knowing exactly what you are going to say, you should know what you need to say then forget about it because in reality, people don't always know exactly what they are going to say. Sometimes they have to think or stumble for the right words to express. This subtlety goes a long way on screen in terms of adding believability and realism.
Back in the early 80s, when I was only about five-years-old, my parents were attending a weekend convention in the city of Huntington, WV. Several of our friends and family were doing the same. We were about two hours away from our hometown, so the adults had grabbed some hotel rooms then we split up: The women went shopping while the dads took us kids to see a movie that was showing in town.