It’s difficult for us to give you any good tips if we don’t know how much you already know about writing screenplays.
If you don’t have it yet, I strongly recommend you get your hands on Syd Field‘s book ”Screenplay”. That’s the single most important book in learning how to write for the movies (or TV). It’s the Bible. More or less all other theories and teachings about writing screenplays are based on Syd Field’s analysis of 100 years of cinema - and millennia of story telling.
It’s best if you follow the classic Three-Act structure with the set-up, confrontation and resolution, while the plot points help you to not get lost. I couldn’t possibly go into detail here - there’s not enough room in the forum… You would have to narrow down your question.
But whatever you do: when you write a screenplay, always think of KIS - Keep It Simple! It’s not a novel, it’s not Shakespeare - it’s a blueprint for a movie. No more, no less.
Entertaining - yes.
Easy to read - yes.
But above all clean, clear and simple.