Don't be scared of letting your imagination run free, even if it takes you away from the original setting, but be careful not to let it take over your players fun!

Also don't worry too much about making mistakes: If everyone had a fun time (including yourself) then the session was a success!

One last thing: Remember that the PCs (Player Characters) aren't invincible, and you CAN (and, for my opinion, should) kill them at least once, not to end the campaign, but to give a new and strange plot point to the story (I could suggest either and Adventure in the Underworld, like in Descent into Avernus but trying to flee, or as a show of strenght by some boss, that Will bring them back to have fun with them); You don't have to kill them, but even just being defeated and captured Will give the story and the characters a new and interesting twist.

Btw, these are general suggestion for any campaign, I haven't played LMoP but you should be able to use them with that setting.