Writing is similar to talking....and not
Why should I take a writing course? My dad always says writing’s not so special - If you can talk you can write!
You’re dad is actually right! I say that too - fairly often! The biggest difference between talkers and writers, especially screenwriters, is whether you actually possess the determination to STOP talking and force yourself to sit down and write.
I assure you all - we (as homo sapiens) know how stories work. We've been telling each other stories for 60,000 - 70,000 maybe even 100,000 years. If you look at the cave art in places like Chauvet - it was ancient people trying to visualize for their audience the thrilling wild mammoth hunt they just witnessed, or something along those lines. We are still doing that today with motion pictures.
What writing classes or seminars do is first of all give you a language or terminology for telling stories. It’s hard to talk to someone else about writing unless you have a common language - so classes can provide some formal names for different portions of story craft - like protagonist, three-act structure and opening scene - montages... that kind of stuff.
The other thing that a formal writing class can do for you is help organize what you already know from years of telling your own stories to friends, classmates and acquaintances. So classes can provide you with terminology for what you do. And can help you realize the inherent structure in the stories you’ve been telling.
And finally, organized writing classes can help harden your resolve to take a seat in front of a computer and put your ideas on paper. Classes aren’t for everyone, but they can provide some useful tools to starting the writing journey. Or they can stoke the fire for when you’re not certain how to continue with what you’ve started.
I hope this helps. And I do wish you good luck with your writing.