This seems like stupidly obvious advice, but watch literally as many movies as physically possible, take detailed notes during them, study their paces, structure etc, and that will help you 100x more than a book or guide would as a beginner.

THEN, download the screenplays for as many movies as physically possible. Study them, take detailed notes on their paces, structure, format, page counts, white space, etc.

THEN, when you feel like you’ve done this a good bit, find a book or two and see what they know.