Ok this movie had a dude in it and an invisible creature (i don't
remember if it was a gremlin or hobgoblin or what) and it was his
friend but nobody believed him that it existed. So it gave him the
ingredients to make a potion that would turn it visible. He made it in
his kitchen and it stunk really bad and when the creature drank it
first his guts were visible, then his skeleton and muscles, and
finally the rest of him. What was the name of that movie?

My best guess is that you may be remembering an episode from the 1980s
version of "The Twilight Zone." In this episode, called "Personal
Demons," a writer (played by veteran character actor Martin Balsam) is
troubled by gremlins or demons that only he can see. Please let me
know if this rings a bell, and I'll be glad to repost it as your
official answer.

im sorry it took so long to answer but no thats not it, this one had
like, a hole in the ground that he went into i think its where he came
from or something and the dude went to visit him. i don't remember
enough right now i'll have to come back later to this one.