Take it one step at a time
Just to make sure that everyone’s on the same page, writer’s block is generally a potentially non-existant condition where a writer just can’t continue writing. There’re many reasons for this and the many, many tips to combat it are everywhere for those who look. I myself have a tip.
Take it one step at a time.
Instead of thinking so much about the end product, just focus on one sentence/thing at a time. For example: hero opens door –> goop falls on his head –> he slips on the goop on the floor –> he ends up on his back –> he sees the ceiling –> there’s a huge spider on the ceiling, dripping spider goop into his face… Even if most of what you get is gibberish, eventually you’ll get some really good gems. Then you can delete all the gibberish and continue with the good stuff.
On the other hand, you can always write anachronically: do the sections you can and want to write about first regardless of what order it’s supposed to be in, but that’s another story.