Your sentence is almost perfect! Here's the original sentence with a small correction for clarity and grammar:
"The forest is like a house with many floors. Squirrels jump high in the trees, bears eat berries below, and little animals hide in the tall grass."
The sentence is correct and easy to understand. It uses simple words and describes different animals in the forest very well. You can keep it exactly as it is!
If you'd like, here is an alternative version with a tiny change for smoother flow:
"The forest is like a house with many floors. Squirrels jump high in the trees, bears eat berries on the ground, and little animals hide in the tall grass."
This just makes it a bit clearer that bears are eating on the ground level.