Can anyone suggest me the best resource to learn comedy screenwriting for movies? I have read sydfield's screenwriting book and learnt a lot from it. But I know that comedy genre follows entirely different structure. I have seen some of the books. But not sure which one to take on! Can anybody help me?
I would suggest Blake Snyder's "Save the Cat" and "Save the Cat Goes to the Movies" as some good starting material. I found them to be very useful for understanding story structures in general, particularly those most common in Hollywood.
Along these lines, I would suggest not just limiting yourself to comedy-specific advice. The best comedy (IMO) takes the rules we are familiar with and shows the ridiculousness of those rules. So it's important to know and understand those rules inside and out, so that you're either making use of them or making fun of them intentionally. Sadly, there's no book to teach you how to have a sense of humor. (Otherwise I know a few people I'd recommend read it!) :)
I highly recommend this book:
As an opening disclaimer, I don't have any actual experience in this area, but I have an opinion that may - or may not - help.
It always bothers me when I read a question asking 'how do I write x/y/z genre / style / etc
The problem is if you go off and find an exceptionally good resource to help you write comedy screenwriting, you won't be the only person reading it, and so you'll end up being one of a whole group of people who read what you read and turned out a write-by-numbers piece. Whoever reads it will quickly spot it and it will head towards the bin.
It will also be unlikely to be funny, because we've all seen them before, the endless stream of hollywood romcom series is horribly similar.
So instead, sit down and start writing, get feedback on what you've written, improve your style, rinse/repeat.
That way you will write something in your style, that hasn't been seen before, and will have a hugely better chance of being taken on by someone.
The technical details are something that can get cleaned up in the edits once the overall thing has been accepted. I can't imagine any studio would expect a perfectly formatted and stylised piece, if only because I would suspect they all have their own styles and formats.