Learn Hardcore Korean: dororeul ttara ttokbaro georeo gamyeon sageoriga nawa. - If you walk straight along the road, you’ll come to an intersection.

도로를 따라 comes from the verb 따르다 (“to follow”) with the object marker -를, so literally “follow the road.” In practice it functions adverbially as along the road or following the road.

Why is 도로 followed by 를?

Because 따라 (from 따르다) is a verb that takes a direct object. The -를 marks 도로 as the thing being followed.

What nuance does 똑바로 add here?

똑바로 is an adverb meaning straight or upright. In this context it means straight ahead, emphasizing that you shouldn’t turn.

Why is it 걸어 가면 and not just 걸으면 or 가면?

걸어 가다 is a compound verb meaning to go on foot.

걸으면 (if you walk) focuses only on walking.
가면 (if you go) could be by any means.
Using 걸어 가면 makes it clear you’re going there by walking.

What role does -면 play in 걸어 가면?

The suffix -면 attaches to a verb stem to express “if” or “when.” Thus 걸어 가면 means “if/when you walk (there).”

What does 사거리가 나와 mean, and why use 나오다?

사거리 is “intersection” (사 four + 거리 street). 나오다 here means “to appear” or “to come out,” so 사거리가 나와 literally says “an intersection appears,” i.e. “you come to an intersection.”

Can I say 도로를 따라 곧장 걸어가면 사거리가 나와 instead?

Yes. 곧장 is another adverb for straight ahead.
도로를 따라 곧장 걸어가면 사거리가 나와 is perfectly natural and has the same meaning.

Why is there no subject in this sentence?

Korean frequently omits subjects when they’re clear from context. Here the implicit subject is you (the person receiving directions).

Could I use 네거리 instead of 사거리?

Yes. 네거리 (“four-way junction” in pure Korean) and 사거리 (the Sino-Korean equivalent) are both common. Many speakers use them interchangeably.