When you move “quickly” to another position in the sentence, it can seem to suggest the watching was quick, not the running. That’s nonsense. But adverbs don’t always modify verbs.

"Nicely" is the adverb here as it describes how the Gorilla Monster is playing with the train. He quickly ate his breakfast. In the sentence above, the adverb 'quickly' appears before the verb 'ate'.

"Nicely" is the adverb here as it describes how the Gorilla Monster is playing with the train. He quickly ate his breakfast. In the sentence above, the adverb 'quickly' appears before the verb 'ate'.