私はローマに住んでいた時に子供でした。
I didn't understand "住んでいた時". I would like a explanation about this structure and a translation.
私はローマに住んでいた時に子供でした。
I didn't understand "住んでいた時". I would like a explanation about this structure and a translation.
私はローマに住んでいた時に子供でした。
When I was in Rome, I was a child.
とき(に) means "when ~". See this article.
As you can see in the link, とき here is just a noun that means "time". So once you have learned how to modify a noun (e.g., using an adjective or a relative clause), you can use various ways to say "when ~".
As pointed out in the comment section, this sentence is a bit unnatural because the main subject (私は) and the main predicate (子供でした) are far apart.
As others have pointed out, the sentence sounds weird. To answer your question:
住む is the verb "to live".
= > 住んで is the "te" form of the verb — a verb form used in many ways.
= > 住んでいる is the "te-iru" form of the verb. This means "living".
= > 住んでいた is the past tense of the "te-iru" form of the verb. This means "was living".
時 is simply "time".
Therefore 住んでいた時 means "the time when I was living".