Learn the correct grammar for a simple sentence describing how an axolotl breathes underwater using its feathery gills.
Let's look at the sentence you gave: 'To breathe underwater, the axolotl has gills that look like feathery branches that stick out from the sides of its head.' This sentence is actually grammatically correct. It clearly explains that an axolotl breathes underwater by using gills. The gills look like feathery branches and they stick out from the sides of its head.
So there is no need to change the grammar. But if we want to make it simpler for a 4-year-old, we could say: "An axolotl breathes underwater with gills. These gills look like feathery branches on its head."