I haven’t seen the movie, but I know the book pretty well.
- There is no appearance of elves at all in the book.
There is more than one appearance of elves in the book.
- You don't ever see any goblins outside of the caverns in the book
The goblins are seen outside their lair more than once.
- The party doesn't enter the cavern by chance like they do in the movie, they planned to go through it all the way along because going in the mountains would be too hazardous (or something in the like, I'm not totally sure)
You’re probably mixing up the Hobbit with FotR. They did not (and would never!) plan to cross the mountains that way.
- The cavern where they find the rare swords and the cavern where they get trouble with goblins, and where gollum live, is the same and only cavern
Nope. One of them is chapter 2, the other is 4-5.
- The giant spiders doesn't appear before the other side of the huge forest, so they should not appear in this movie.
Well, it happens roughly halfway into the book, so it wouldn’t take too much fudging.
Now I imagined the dwarves being really tiny, something about like 50cm high, much smaller than the hobbit. In the movie they almost appear like humans, considering there is no human it's hard to make a comparison but they don't look tiny at all. This could have been my imagination though - I don't remember how tolkien described them. I also imagined them as funny creatures, something very far from the badass look they have in the movie.
4 paragraphs in: “what is a hobbit? I suppose hobbits need some description nowadays, since they have become rare and shy of the Big People, as they call us. They are (or were) a little people, about half our height, and smaller than the bearded Dwarves.”