"I live on the longest road."
Translation:저는 제일 긴 길에 살아요.
You can actually use both 에 and 에서 in this case. You can use the static locative particle (에) and the dynamic locative particle (에서) when you use the verb 살다.
저는 미국에 살아요=저는 미국에서 살아요 (I live in the US)
Though there is a very subtle difference in meaning, both sentences can be used interchangeably.
I suppose you can... Text below is taken from the notes of this lesson.
The superlative form in Korean is formed using 가장 or 제일 plus the adjective/descriptive verb. Both can be used interchangeably, but 가장 means "the most," and 제일 means "number one."
Usually the phrase is 제일/가장 + Modifier form + Noun.
For example, 제일 맛있는 음식=the most delicious food
When forming a superlative in English, the noun is not always used, for example "This book is the best." In Korean, you would translate that as 이 책은 제일 좋은 책이에요 "This book is the best book" or 이 책은 제일 좋은 것이에요 "This book is the best one." Unlike in English where we actively seek to avoid repeating the noun, it is completely okay in Korean.