Answer:
It is a dangling modifier.
Explanation:
I'll assume that the bolded phrase was before becoming a yo-yo expert.
A modifier is a word that gives more information about another word. A dangling modifier is a modifier that could be misinterpreted as being associated with a word other than the one intended. Accordingly, in the given sentence, we could think that the phrase before becoming a yo-yo expert could refer to the training classes instead of Perry the Platypus.
