The sentence is an example of figurative language as it uses a type of language that goes beyond the literal meanings of the words in order to make ideas more colorful and meaningful: The speaker does not literally make one step per minute, this idea is expressed this way so it could be more colorful and effective than to simply say "I walked very slowly".
Moreover, this sentence is also an example of hyperbole (which is a type of figurative language) because it involves an exaggeration of ideas. To make one step per minute is extremely slow, unrealistic and obviously false. The speaker tells it this way for the sake of emphasis.
