Fantasy, another world, swamp, strange creatures
 

I found already. It's "Fungus the Bogeyman" - sounds like Shrek parody. :D:D:D
https://www.imdb.com/title/tt0361642/

I have next interesting riddle. My friend watched it in 2003-2010.

The film is set in modern times and it is about children who finds a world underground and there live (green probably) creatures. Then, it is a scene that they came to the surface at night and bushwhacked around the house, looking for food, and at the end they left such sticky green footprints all over the house. I think there was something like that. There was also a scene in which one of the creatures pokes its head out of a barrel of manure or some black liquid. They, in the daytime, I think, were somehow hiding above the ground so they wouldn't be seen. In another scene, a girl or boy puts a snail in a thermos of man. In another scene in this strange world underground, a family of these creatures hides the children in their house by covering the entrance to the living room with a wardrobe. The policeman comes in and ask what happened to the living room, and they say they did some rearranging. The policemen entered the living room but the children are gone, because they hid behind the window. He still remembers the scene in this world underground how they wanted to somehow hide these children from the police and they told the policeman that down in the mud or water someone needed help. Then he came down, and when he was at the bottom they said that this person had already come out from the other side and they left him there.

This village was a bit like Venice, only instead of water there was a swamp. It isn't "Little monsters" (1988), but something after 2000's.