1
I saw a small mouse in the garage.
Sign "mouse" by brushing your index finger across your nose, then use your hands to show a small size while squinting slightly to emphasize how tiny the animal is.
2
My cat loves to chase mice.
Sign "cat," then "mouse," followed by the sign for "chase" to show the playful or hunting action between the two animals.
3
My computer mouse is broken.
Sign "computer," then use the sign for "mouse" at your nose. Context will make it clear to the person you are talking to that you mean the tech accessory, not the animal.