This pattern is written in English and uses US crochet terms.

Koala rattle is around 4.3 inches (11 cm) when finished.

The pattern uses:

• 1.75 crochet hook
• yarn weight fine
• wooden ring diameter is 2.1 inches (5.4 cm).

This pattern is for the medium level crocheters but if you are ready to try I am always ready to help.
You should know basic crochet stitches including

chain stitch,
slip stitch,
single crochet,
decrease,
increase,
magic ring.