Everyone has shared incredible advice so far and I wanna add on with some of mine own. My MSPFA isn’t really the standard format (like what you would normally expect) but I hope some of this helps! And SORRY FOR how long it will be… Oops
It’s always good to plan out first. This helps make it way easier. For example, what tone will it have? What a your characters like? What are their thoughts on each other? For the story you should plan out, at the very least, basic plot beats to help guide you along. If you do suggestions this can help especially because you can choose ones that can lead to plot points or specific things you wanna bring up.
For me how I try to deal with pacing (my biggest issue) I sometimes ask my friend to proofread my script to get second opinions!!! I have a huge script written out for my adventure but like you can just write down your ideas quickly and ask for people to read that instead for second opinions.
If you have the whole plot already (like you mentioned here) I recommend writing down every big part of it down so you can figure out how you can get to each part. This can also help with pacing ?? Probably ?? That’s how I go about writing mine anyway. It helps me keep in mind all the important junk so I’m on track.